单选题Why does life on earth depend much on the oceans?ASea plants produce most of the oxygen in the atmosphere.BCarbon dioxide is converted into oxygen in oceans.CThe oceans provide an invaluable food resource.DProductivity of fisheries can feed 80 million people.
单选题
Why does life on earth depend much on the oceans?
A
Sea plants produce most of the oxygen in the atmosphere.
B
Carbon dioxide is converted into oxygen in oceans.
C
The oceans provide an invaluable food resource.
D
Productivity of fisheries can feed 80 million people.
参考解析
解析：
录音的首句指出地球上的生命最终都要依靠覆盖地球71%的海洋，其中的原因是广阔的水域提供了大气层中大部分的氧气，同时微型植物每天吸收数百万吨的二氧化碳(These vast basins of water provide most of the oxygen in our atmosphere, and microscopic plants absorb millions of tons of carbon dioxide each day.)，还有就是海洋也含有珍贵的食物资源，每天通过渔业提供八千万公吨的食物(The seas also hold a precious food resource, providing 80 million metric tons of food a year through fishing)，所以只有C项正确。
录音的首句指出地球上的生命最终都要依靠覆盖地球71%的海洋，其中的原因是广阔的水域提供了大气层中大部分的氧气，同时微型植物每天吸收数百万吨的二氧化碳(These vast basins of water provide most of the oxygen in our atmosphere, and microscopic plants absorb millions of tons of carbon dioxide each day.)，还有就是海洋也含有珍贵的食物资源，每天通过渔业提供八千万公吨的食物(The seas also hold a precious food resource, providing 80 million metric tons of food a year through fishing)，所以只有C项正确。
相关考题：
Most animals have little connection with animals of different kind, unless they hunt them for food. Sometimes, however, two kinds of animals come together in a partnership ( 伙伴关系 ) which does good to both of them. You may have noticed some birds sitting on the backs of sheep. This is not because they want a ride, but because they find easy food in the parasites (寄生虫 ) on sheep. The sheep allow the birds to do so because they remove the cause of discomfort. So although they can manage without each other, they do better together.Sometimes an animal has a plant partner. The relationship develops until the two partners cannot manage without each other. This is so in the corals ( 珊瑚 ) of the sea. In their skins they have tiny plants act as "dustman", taking some of the waste products form. the corals and giving in return oxygen which the animal needs to breathe. If the plants are killed, or are ever prevented from lighting so that they cannot live normally, the corals will die.1、Some birds like to sit on a sheep because ( ).A、they can eat its parasitesB、 they depend on the sheep for existenceC、 they enjoy traveling with the sheepD、 they find the position most comfortable2、The underlined word "they" in the last sentence of the first paragraph refers to ( ).A、birds and parasitesB、birds and sheepC、parasites and sheepD、sheep, birds and parasites3、What does the second paragraph mainly discuss? ( )A、Some animals and plants depend on each other for existence.B、 Some animals and plants develop their relationship easily.C、 Some plants depend on each other for fooD、 Some animals live better together.4、What does this article talk about? ( )A、Two kinds of animals for a partnership.B、Most animals only have connection with animals.C、The connection between the living things.D、Corals have some connection with plants.
AWhy do plants grow in some places and not in others? Why does some land have so much growing on it，while other land has almost no plants growing on it at all?To grow plants need several things． One is warmth． In very cold places almost nothing grows． Plants also need water． In very dry parts of the earth only a few unusual plants can grow． That's why dry deserts everywhere are almost not covered by trees or grass．Plants must also have a place in which to f，ut down their roots and grow． They find it diffi-culr to grow on hard land． The town is built on hard land． The plants here have only the soil found between the cracks of the stones Io grow in．Another thing plants must have before they can grow is food．Whar will happen if we try to make things grow on the sandy beach? A few plants，such as beach grass，will grow in sand，L ut most plants won-t． Even if the weather is warm enough．and we water the plants each day． Many of them will die because the sand on this beach has al-most no food for plants．( )21． According to the passage，plants need _________ things to grow well．A． twoB． threeC． fourD． five
24． The reason why most plants can’t grow on the sandy beach is thatA． there isn't enough sunlightB． there is too much waterC． it is too crowded thereD． it has little food for plants
Which statement concerning carbon dioxide is FALSE ________．A.It displaces the oxygen in the airB.It cannot be seenC.It cannot be smelledD.It is safe to use near personnel in a confined space
Which statement about entry into a space that has been sealed for a long time is TRUE ________．A.A tank that has been used to carry hazardous liquids should be tested for oxygen content，toxicity，and explosive gasesB.You can safely enter the space without a breathing apparatus if the oxygen content exceeds 14%C.The natural ventilation through the installed vents is sufficient to provide the proper oxygen contentD.The heat of the sun on upper ballast tanks，such as in a bulk carrier，may generate carbon monoxide
What could result in an incorrect oxygen concentration reading on the oxygen indicator ________．A.Exposure to carbon dioxide for no more than 1 minuteB.Exposure to carbon dioxide for more than 10 minutesC.Exposure to a very low concentration of sulfur dioxide for no more than 2 minutesD.None of the above
Passage 2If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.On Venus there is a lot of__________.A. waterB. carbon dioxideC. carbon monoxideD. oxygen
Passage 2If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus. Man can eventually land on Venus only when__________.A. the algae have done their workB. the atmosphere becomes coolerC. there is oxygenD. it rains there
Passage 2If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.CarlSagan believes that Venus might be colonized from earth because__________.A. it might be possible to change its atmosphereB. its atmosphere is the same as the earth'sC. there is a good supply of water on VenusD. the days on Venus are long enough
Passage 2If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.In the long run, the most difficult problem caused by population growth on earth will probably be the lack of__________.查看材料A．foodB．oilC．spaceD．resources
Passage 2If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.Algae are plants that can__________.查看材料A．live in very hot temperaturesB．live in very cold temperaturesC．manufacture oxygenD．all of the above
Passage 2If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet. By the middle of the 21st century, if present trends continue, we will have used up all the oil that drives our cars, for example. Even if scientists develop new ways of feeding the human race, the crowded conditions on earth will make it necessary for us to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however, has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible to change the atmosphere of Venus and so create a new world almost as large as earth itself. The difficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres and at the same time produce oxygen, should be bred in conditions similar to those on Venus. As soon as this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venus and fire the rockets into the atmosphere. In a fairly short time, the algae will break down the carbon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before man can set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planet will still be too hot for men to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.CarlSagan believes that Venus might be colonized from earth because__________.查看材料A．it might be possible to change its atmosphereB．its atmosphere is the same as the earth'sC．there is a good supply of water on VenusD．the days on Venus are long enough
共用题干第一篇Putting Plants to WorkUsing the power of the sun is nothing new.People have had solar-powered calculators and buildings withsolar panels（太阳能电池板）for decades. But plants are the real experts. They' ve been using sunlight as anenergy source for billions of years.Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide（二氧化 碳）,and water into sugarsand starche（淀粉）,stored energy that the piants can use. This conversion process is called photosynthesis (光合作用）Unfortunately, unless you' re a plant, it's difficult and expensive to convert sunlight into storable energy. That's why scientists are taking a closer look at exactly how plants do it.Some scientists are trying to get plants,or biological cells that act like plants, to work as very small photosynthesic power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden. Cobo.,is working with green algae（水藻）.She's trying to trick them into producing hydrogen instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficient- ly ,the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity.The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthe- sis , plants normally make sugars or strchds. "But under certain conditions,a lot of algae are able to use the sunlight energy not to store starch , but to make hydrogen."Ghirardi says. For example ,algae will produce hy-drogen in an airfree environment. It' s the oxygen in the air that prevents algae from making hydrogen most of the time.Working in an airfree environment, however, is difficult. It's not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate（硫酸盐） from the environment that the algae grow in, they will make hydrogen instead of sugars,even when air is present.Unfortunately, removing the sulfate also makes the algae's cells work very slowly,and not much hydrogen is produced. Still ,the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work,they may be able to speed the cells' activity and produce larger quantities of hydrogen.The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says,and they can grow almost anywhere:"You can grow them in a reactor, in a pond. You can grow them in the ocean. There's a lot of flexibility in how you can use these organisms." Algae are able to use solar energy to produce hydrogen when_______________.A:they are grown in narrow-necked bottlesB:there is no oxygen in the airC:there is enough oxygen in the airD:enough starch is stored
根据下列内容，回答196-200题。If the population of the earth goes on increasing at its present rate, there will eventually notbe enough resources left to sustain life on the planet. By the middle of the 21st century, if presenttrends continue, we will have used up all the oil that drives our cars, for example. Even if scien-tists develop new ways of feeding the human race, the crowded conditions on earth will make itnecessary for us to look for open space somewhere else. But none of the other planets in our solarsystem are capable of supporting life at present. One possible solution to the problem, however,has recently been suggested by an American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are completely exhausted it will be possible tochange the atmosphere of Venus and so create a new world almost as large as earth itself. The dif-ficulty is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms, which can live in extremely hot or cold atmospheres andat the same time produce oxygen, should be bred in conditions similar to those on Venus. As soonas this has been done, the algae will be placed in small rockets. Spaceships will then fly to Venusand fire the rockets into the atmosphere. In a fairly short time, the algae will break down the car-bon dioxide into oxygen and carbon.When the algae have done their work, the atmosphere will become cooler, but before mancan set foot on Venus it will be necessary for the oxygen to produce rain. The surface of the planetwill still be too hot for men to land on it but the rain will eventually fall and in a few years some-thing like earth will be reproduced on Venus.In the long run, the most difficult problem caused by population growth on earth willprobably be the lack of __________.A.foodB.oilC.spaceD.resources
If the population of the earth goes on increasing at its present rate, there will eventually not be enough resources left to sustain life on the planet.By the middle of the 21st century,if present trends continue, we will have used up all the oil that drives our cars,for example.Even if scientists develop new ways of feeding the human race,the crowded conditions on earth will make it necessary for lus to look for open space somewhere else. But none of the other planets in our solar system are capable of supporting life at present. One possible solution to the problem, however,has recently been suggested by American scientist, Professor Carl Sagan.Sagan believes that before the earth's resources are compleetely exhausted it will be possible to change the atmophere of Venus and so create a new world almost as large as earth itself. The difficult is that Venus is much hotter than the earth and there is only a tiny amount of water there.Sagan proposes that algae organisms that can live in extremely hot or cold atmospheres and at the same time produce oxygen,should be bred in condition similar to those on Venus.As soon as this has been done, the algae will be placed in small rockets. Spaceship will then fly to Venus and fire the rockets into the atmosphere .In a fairly short time, the alge will break down the carbon dioxide into oxygen and carbon.When the algae have done theri work, the atmosphere will become cooler,but befor man can set foot on Venus it will be neccessary for the oxygen to produce rain. The surface of the planet will still be too hot for man to land on it but the rain will eventually fall and in a few years something like earth will be reproduced on Venus.Inte long run, the most insoluble problem caused by population growth on earth will probably be the lack of ______.a.food b.oilc.spaced.resources
共用题干第一篇Plant GasScientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.Which of the following about methane is not mentioned in the passage?A:Plants growing in soil release methane.B:Plants growing in water release methane.C:Soil microbes consume methane.D:Microbes in plants produce methane.
共用题干第一篇Plant GasScientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.What was scientists' understanding of methane?A:It was produced from plants.B:It was not a greenhouse gas.C:It was produced in oxygen-free environments.D:It traps more heat than any other greenhouse gas.
共用题干第一篇Plant GasScientists have been studying natural sources of methane（甲烷，沼气）for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist（地球化学家）at the Max Planck Institute for Nuclear Physics in Heldelberg,Germany. Now Keppler and his colleagues find that plants,from grasses to trees,may also be sources of the greenhouse gas.This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment.Previously,researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes（微生物）need to be in environments without oxygen to produce methane.Methane is a greenhouse gas, like carbon dioxide.Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming.In its experiments, Keppler's team used sealed chambers（室，房间；腔）that contained the same concentration of oxygen that Earth's atmosphere has.They measured the amounts of methane that were released by both living plants and dried plant material,such as fallen leaves.With the dried plants,the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C.At 30 degrees C.,they found,a gram of dried plant material released up to 3 nanograms（微克）of methane per hour(One nanogram is a millionth of a gram). With every 10-degree rise in temperature,the amount of methane released each hour roughly doubled.Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight.Because there was plenty of oxygen available,it's unlikely that the types of bacteria(bacterium的复数，细菌）that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions.That's another strong sign that the gas came from the plants and not soil microbes.The new finding is an"interesting observation,"says Jennifer Y. King,a biogeochemist（生物地球化学家）at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane,they may prevent plant-produced methane from reaching the atmosphere.Field tests will be needed to assess the plant's influence,she notes.To test whether plants are a source of methane,the scientists created_______.A:an oxygen-free environmentB:an environment with the same concentration of oxygen as the Earth hasC:a carbon dioxide-free environmentD:an environment filled with the greenhouse gas
An Essential Scientific ProcessAll life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet. 词汇：nutrient n.营养物 ganism n.生物体，有机体carbon dioxide n.二氧化碳chloplast n.叶绿体molecule n.分子vap n.水蒸气oxygen n.氧气 photosynthesis n.光合作用chlophyll n.叶绿素glucose n.葡萄糖cease v.停止 注释：1.Then animals feed upon the plants.动物以植物为食。 练习：5.Another good title f this passage would beA.Oxygen Carbon Dioxide.B.Plants Their Roots.C.How Photosynthesis Wks.D.Why Our Earth Needs Water.
An Essential Scientific ProcessAll life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet. 词汇：nutrient n.营养物 ganism n.生物体，有机体carbon dioxide n.二氧化碳chloplast n.叶绿体molecule n.分子vap n.水蒸气oxygen n.氧气 photosynthesis n.光合作用chlophyll n.叶绿素glucose n.葡萄糖cease v.停止 注释：1.Then animals feed upon the plants.动物以植物为食。 练习：4.This passage is primarily developed byA.explaining a process.B.telling a sty.C.comparing contrasting.D.convincing the reader of plants’ imptance.
An Essential Scientific ProcessAll life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet. 词汇：nutrient n.营养物 ganism n.生物体，有机体carbon dioxide n.二氧化碳chloplast n.叶绿体molecule n.分子vap n.水蒸气oxygen n.氧气 photosynthesis n.光合作用chlophyll n.叶绿素glucose n.葡萄糖cease v.停止 注释：1.Then animals feed upon the plants.动物以植物为食。 练习：1.In the first paragraph，the wd “excess” meansA.heavy.B.extra.C.green.D.liquid.
An Essential Scientific ProcessAll life on the earth depends upon green plants. Using sunlight, theplants produce their own food. Then animals feed upon the plants. They take inthe nutrients the plants have made sted. But that’s not all.Sunlight also helps a plant produce oxygen. Some of the oxygen is used by theplant, but a plant usually produces me oxygen than it uses. The excess oxygenis necessary f animals other ganisms to live.The process of changing light into food oxygen is calledphotosynthesis. Besides light energy from the sun, plants also use water carbon dioxide. The water gets to the plant through its roots. The carbondioxide enters the leaves through tiny openings called stomata. The carbondioxide travels to chloplasts, special cells in the bodies of green plants.This is photosynthesis takes place. Chloplasts contain the chlophyllsthat give plants their green col. The chlophylls are the molecules thattrap light energy. The trapped light energy changes water carbon dioxide toproduce oxygen a simple sugar called glucose.Carbon dioxide oxygen move into out of the stomata. Watervap also moves out of the stomata. Me than 90 percent of water a planttakes in through its roots escapes through the stomata. During the daytime, thestomata of most plants are open. This allows carbon dioxide to enter the leavesf photosynthesis. As night falls, carbon dioxide is not needed. The stomataof most plants close. Water loss stops.If photosynthesis ceased, there would be little food other ganicmatter on the earth. Most ganisms would disappear. The earth’s atmospherewould no longer contain oxygen. Photosynthesis is essential f life on ourplanet. 词汇：nutrient n.营养物 ganism n.生物体，有机体carbon dioxide n.二氧化碳chloplast n.叶绿体molecule n.分子vap n.水蒸气oxygen n.氧气 photosynthesis n.光合作用chlophyll n.叶绿素glucose n.葡萄糖cease v.停止 注释：1.Then animals feed upon the plants.动物以植物为食。 练习：2.Which of the following does not move through a plant’s stomata?A.Carbon dioxide. B.Water vap.C.Oxygen. D.Food.
单选题Why does life on earth depend much on the oceans?ASea plants produce most of the oxygen in the atmosphere.BCarbon dioxide is converted into oxygen in oceans.CThe oceans provide an invaluable food resource.DProductivity of fisheries can feed 80 million people.
填空题Glucose can be completely broken down into carbon dioxide and water when oxygen is present in the process called aerobic respiration.____
单选题Carbon dioxide flooding system is used for extinguishing fires because it reduces the concentration of oxygen in the air to（）.Aflashing pointBcombustion pointCauto-ignition pointDlower explosive limit
问答题Practice 5 The world's oceans are slowly getting more acidic, say scientists. The researchers from California say the change is taking place in response to higher levels of carbon dioxide in the atmosphere. The lowering of the waters' pH value is not great at the moment but could pose a serious threat to current marine life if it continues, they warn. Ken Caldeira and Michael Wickett, from the Lawrence Livermore National Laboratory, report their concerns in the journal Nature. Increasing use of fossil fuels means more carbon dioxide is going into the air, and most of it will eventually be absorbed by seawater. Once in the water, it reacts to form carbonic acid. Scientists believe that the oceans have already become slightly more acidic over the last century. But these researchers have tried to predict what will happen in the future by combining what we know about the history of the oceans with computer models of climate change. "This level of acidity will get much more extreme in the future if we continue releasing CO2 into the atmosphere," said Dr Caldeira. "And we predicted amounts of future acidity that exceed anything we saw over the last several hundred million years, apart from perhaps after rare catastrophic events such as asteroid impacts." If carbon dioxide release continues unabated, ocean pH could be reduced by as much as 0.77 units, the authors warn. It is not absolutely clear what that means for marine life, however. Most organisms live near the surface, where the greatest pH change would be expected to occur, but deep-ocean lifeforms may be more sensitive to pH changes. Coral reefs and other organisms whose skeletons or shells contain calcium carbonate may be particularly affected, the team speculate. They could find it much more difficult to build these structures in water with a lower pH. In recent years some people have suggested deliberately storing carbon dioxide from power stations in the deep ocean as a way of curbing global warming. But Dr Caldeira said that such a strategy should now be re-considered. "Previously, most experts had looked at ocean absorption of carbon dioxide as a good thing — because in releasing CO2 into the atmosphere we warm the planet; and when CO2 is absorbed by the ocean, it reduces the amount of greenhouse warming.
单选题Why should you wear a self-contained breathing apparatus before entering the engine room after the fixed CO2 system has been discharged to combat a major fire?（）ABecause carbon dioxide dilutes the oxygen concentration in the atmosphere and may cause asphyxiationBBecause carbon dioxide breaks down in a fire into carbon monoxide which may cause blood poisoning in the person breathing this gasCBecause carbon dioxide is a colorless and odorless gas that becomes highly toxic in the presence of high temperatures and will quickly incapacitate a person exposed to this gasDThis action is unnecessary as carbon dioxide is not poisonous nor toxic but is a relatively harmless gas
单选题Plants use the carbon, along with sunlight, for growth, and （） oxygen into the atmosphere in a process known as photosynthesis.ArelieveBrelateCreleaseDretain