There（）three plants in the corners of the room.A、isB、areC、have
There（）three plants in the corners of the room.
- A、is
- B、are
- C、have
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Go straight,() and you will find a sign for the toilet. A、three minutes' awayB、three minutes' walkC、three minute's awayD、three minute's walk
CPlants can’t communicate by moving or making sounds, as most animals do. Instead, plants produce volatile compounds, chemicals that easily change from a liquid to a gas. A flower’s sweet smell, for example, comes from volatile compounds that the plant produces to attract insects such as bugs and bees.Plants can also detect volatile compounds produced by other plants. A tree under attack by hungry insects, for instance, may give off volatile compounds that let other trees know about the attack, In response, the other trees may send off chemicals to keep the bugs away- or even chemicals that attract the bugs’ natural enemies.Now scientists have created a quick way to understand what plants are saying: a chemical sensor(传感器) called an electronic nose. The “e-nose” can tell compounds that crop plants make when they’re attacked. Scientists say the e-nose could help quickly detest whether plants are being eaten by insects. But today the only way to detect such insects is to visually inspect individual plants. This is a challenging task for managers of greenhouses, enclosed gardens that can house thousands of plants.The research team worked with an e-nose that recognizes volatile compounds. Inside the device, 13 sensors chemically react with volatile compounds. Based on these interactions, the e-nose gives off electronic signals that the scientists analyze using computer software.To test the nose, the team presented it with healthy leaves from cucumber, pepper and tomato plants, all common greenhouse crops. Then the scientists collected samples of air around damaged leaves from each type of crop. These plants had been damaged by insects, or by scientists who made holes in the leaves with a hole punch (打孔器).The e-nose, it turns out, could identify healthy cucumber, pepper and tomato plants based on the volatile compounds they produce. It could also identify tomato leaves that had been damaged. But even more impressive, the device could tell which type of damage – by insects or with a hole punch – had been done to the tomato leaves.With some fine tuning, a device like the e-nose could one day be used in greenhouses to quickly spot harmful bugs, the researchers say. A device like this could also be used to identify fruits that are perfectly ripe and ready to pick and eat, says Natalia Dudareve, a biochemist at Purdue University in West Lafayette, Ind. who studies smells of flowers and plants. Hopefully, scientists believe, the device could bring large benefits to greenhouse managers in the near future.49. We learn from the text that plants communicate with each other by______.A. making some sounds B. waving their leavesC. producing some chemicals D. sending out electronic signals
The new gym is _________ as the old one.A、three times as largeB、three times the sizeC、three times larger thanD、as three times large
The students must finish the test in(). A、three quarters of an hour timeB、three quarter's of an hour timeC、three quarters of an hour's timeD、three quarters'of an hour's time
The wealthy doctor has a __________ daughter.A、three-years-oldB、three years’ oldC、three-year-oldD、three-year old
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
BScientists are trying to make the deserts into good land again． They want to，bring water to the deserts． But more and more places of the earth is becoming deserts all the time， Scientists may not be able to change the deserts． Scientists think that people make deserts． People are do-ing bad things to the earth．Some places on the earth don-t get very much rain． But they still don-t become deserts．This is because some green plants are growing there． Small green plants and grass are very helpful to dry places． Plants don't let the wind blow the earth away． When 8 little bit of rain falls，the plants hold the water． Without plants，the land can become a desert much more easily．( )26． Why can the land become a desert?A． Because some places don't get very much rain．B． Because plants don-t let the hot sun make the earth even drier．C． Because people don't keep the earth well．D． Because scientists haven-t learnt enough about the deserts．
共用题干Microchip Research Center CreatedA research center has been______(51)in this Far Eastern country to develop advanced microchip production technology.The center,which will start out with about US$14 million,will help the country develop its chip industry without always depending on imported technology.The center will make use of its research skills and______(52)to develop new technology for _______(53)chip plants.The advent of the center will possibly free the country from the_______(54) that it is always buying almost-outdated technologies from other countries,said the country's flagship chipmaker.______(55),chip plants in this country are in a passive situation because many foreign governments don't allow them to______(56)the most advanced technologies,fearing they will be used for______(57) purposes.Moreover,the high licensing fees they have to pay to technology providers are also an important _(58)for their decision of self-reliance.As mainstream chip production technology______(59)from one generation to the next every three to five years,plants with new technology can make more powerful chips at lower costs,while plants with______(60)equipment,which often cost billions of dollars to build,will be______(61)by the maker.More than 10 chip plants are being built,each costing millions of US dollars.The majority of that money goes to overseas equipment______(62)and technology owners-mainly______(63)Japan and Singapore.Should the new center play a major role in improving the situation in the industry,the country admits the US $14 million investment is still rather small.This country is developing______(64)technologies.Most of the investment will be spent on setting_______(65)with technology and intellectual property owners.60._________A:outdatedB:outgoing C:outward D:fashionable
In trying to accumulate knowledge about the universe and to find common factors which underline and account for the facts that he knows,the scientist often chooses the method of the“controlled experiment.”If he wants to find out the effect of light（ ）growing plants,he takes many plants，as alike as possible.A.onB.ofC.byD.to
Next week, the German Chancellor will come to China for a___________visit.A.three daysB.three-dayC.three day'sD.three-days
共用题干“Salty” Rice Plant Boosts HarvestsBritish scientists are breeding a new generation of rice plants that will be able to grow in soil containing salt water. Their work may enable abandoned farms to become productive once more.Tim Flowers and Tony Yeo,from Sussex University's School of Biological Sciences,have spent several years researching how crops,such as rice,could be made to grow in water that has become salty.The pair have recently begun a three-year programme,funded by the Biotechnology and Biological Sciences Research Council,to establish which genes enable some plants to survive salty conditions. The aim is to breed this capability into crops,starting with rice.It is estimated that each year more than 10m hectares（公顷）of agricultural land are lost because salt gets into the soil and stunts（妨碍生长）plants. The problem is caused by several factors. In the tropics , mangroves（红树林）that create swamps（沼泽）and traditionally formed barriers to sea water have been cut down .In the Mediterranean,a series of droughts have caused the water table to drop,allowing sea water to seep（渗透）in. In Latin America , irrigation often causes problems when water is evaporated（蒸发）by the heat , leaving salt deposits behind.Excess salt then enters the plants and prevents them functioning normally.Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive.To overcome these problems,Flowers and Yeo decided to breed rice plants that take in very little salt and store what they do absorb in cells that do not affect the plants' growth.They have started to breed these characteristics into a new rice crop,but it will take about eight harvests before the resulting seeds are ready to be considered for commercial use.Once the characteristics for surviving salty soil are known,Flowers and Yeo will try to breed the appropriate genes into all manners of crops and plants.Land that has been abandoned to na- ture will then be able to bloom again,providing much needed food in the poorer countries of the world. The attitude of the author towards the research project is______.A: positiveB: negativeC: suspiciousD: indifferent
共用题干“Salty” Rice Plant Boosts HarvestsBritish scientists are breeding a new generation of rice plants that will be able to grow in soil containing salt water. Their work may enable abandoned farms to become productive once more.Tim Flowers and Tony Yeo,from Sussex University's School of Biological Sciences,have spent several years researching how crops,such as rice,could be made to grow in water that has become salty.The pair have recently begun a three-year programme,funded by the Biotechnology and Biological Sciences Research Council,to establish which genes enable some plants to survive salty conditions. The aim is to breed this capability into crops,starting with rice.It is estimated that each year more than 10m hectares（公顷）of agricultural land are lost because salt gets into the soil and stunts（妨碍生长）plants. The problem is caused by several factors. In the tropics , mangroves（红树林）that create swamps（沼泽）and traditionally formed barriers to sea water have been cut down .In the Mediterranean,a series of droughts have caused the water table to drop,allowing sea water to seep（渗透）in. In Latin America , irrigation often causes problems when water is evaporated（蒸发）by the heat , leaving salt deposits behind.Excess salt then enters the plants and prevents them functioning normally.Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive.To overcome these problems,Flowers and Yeo decided to breed rice plants that take in very little salt and store what they do absorb in cells that do not affect the plants' growth.They have started to breed these characteristics into a new rice crop,but it will take about eight harvests before the resulting seeds are ready to be considered for commercial use.Once the characteristics for surviving salty soil are known,Flowers and Yeo will try to breed the appropriate genes into all manners of crops and plants.Land that has been abandoned to na- ture will then be able to bloom again,providing much needed food in the poorer countries of the world. Flowers and Yeo have started a program______.A: to find ways to prevent water pollutionB: to identify genes that promote growth in salty soilC: to breed rice plants that taste saltyD: to find ways to remove excessive salt from soil
共用题干“Salty” Rice Plant Boosts HarvestsBritish scientists are breeding a new generation of rice plants that will be able to grow in soil containing salt water. Their work may enable abandoned farms to become productive once more.Tim Flowers and Tony Yeo,from Sussex University's School of Biological Sciences,have spent several years researching how crops,such as rice,could be made to grow in water that has become salty.The pair have recently begun a three-year programme,funded by the Biotechnology and Biological Sciences Research Council,to establish which genes enable some plants to survive salty conditions. The aim is to breed this capability into crops,starting with rice.It is estimated that each year more than 10m hectares（公顷）of agricultural land are lost because salt gets into the soil and stunts（妨碍生长）plants. The problem is caused by several factors. In the tropics , mangroves（红树林）that create swamps（沼泽）and traditionally formed barriers to sea water have been cut down .In the Mediterranean,a series of droughts have caused the water table to drop,allowing sea water to seep（渗透）in. In Latin America , irrigation often causes problems when water is evaporated（蒸发）by the heat , leaving salt deposits behind.Excess salt then enters the plants and prevents them functioning normally.Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive.To overcome these problems,Flowers and Yeo decided to breed rice plants that take in very little salt and store what they do absorb in cells that do not affect the plants' growth.They have started to breed these characteristics into a new rice crop,but it will take about eight harvests before the resulting seeds are ready to be considered for commercial use.Once the characteristics for surviving salty soil are known,Flowers and Yeo will try to breed the appropriate genes into all manners of crops and plants.Land that has been abandoned to na- ture will then be able to bloom again,providing much needed food in the poorer countries of the world. Which of the following is NOT mentioned as a cause of the problem discussed in the passage?A: Natural barriers to sea water have been destroyed.B: The water table has gone down after droughts.C: Sea level has been continuously rising.D: Evaporation of water leaves salt behind.
单选题With reference to a rotary vane steering gear system, which one of the following statements is true?（）AThe three moving vanes and the three fixed vanes form three pressure chambersBThe three moving vanes and the three fixed vanes form six pressure chambersCThe three moving vanes and the three fixed vanes form nine pressure chambersDThe three moving vanes and the three fixed vanes form twelve pressure chambers
单选题Which of the following is NOT among the solutions to the lack of sewage water treatment plants?ACooperation with other organizations.BCooperation with the World Bank.CTwo projects about treatment plants for sewage waters in Vlore and Pogradec.DTo control the waste water discharged.
多选题Consider each of the choices separately and select all that apply. Which of these can be inferred from the fact that the French built orangeries for certain tropical plants?AGreenhouses may be used to keep plants at a moderate temperatureBThe climate of France is unsuited to growing tropical plants outdoors.CLouis ⅩⅣ was a frequent and enthusiastic traveler to Africa and Asia
单选题Fertilizer will（）the growth of these tomato plants.AaccomplishBaccelerateCaccumulateDaccount
单选题Why does the author call lichens pioneers?ABecause they developed so early in the history of the planet.BBecause of their primitive structure.CBecause they prepare soil for other plants.DBecause they were the first plants to live in Antarctica.
单选题How should we understand the richness of these three civilizations according to the passage?AIt meant people’s ability to produce commodities.BIt meant people’s ability to domesticate plants and animals.CIn population it meant the ability to raise a ruling class.DIn population it meant the ability to draw other peoples to the area.
单选题The most common forms of main drive used on deck auxiliaries are （）.Asteam plants, electric motors and compressed airBdiesel engine, hydraulic machinery and compressed airCsteam plants, electric motors and hydraulic machineryDdiesel engines, steam plants and hydraulic machinery