At the first sight the planet Mars does not appear very welcome to any kind of life．It has very little oxygen and water,the temperature at night is below-50~Cand winds of 100 miles per hour cause severe dust storms．However,the surface of the planet seems to show that water flowed across it some time in the past,and it is believed that there is enough ice at the poles to cover the planet with water if it melts．Although there is no life on the Mars now,some scientists think that there may have been some form of life long time ago．At that time,the planet had active volcanoes;the atmosphere was thicker and warmer;and there was water．In fact,in some ways the Mars may have been similar to the Earth,where life exists.Some people believe that the Mars could support life in the future if the right conditions were produced．The first step would be to warm the planet using certain gases which trap the Sun's heat in the planet's atmosphere．With warmth,water and carbon dioxide(二氧化碳),simple plants could begin to grow．These plants could slowly make the Mars more suitable for living．It is estimated that the whole process might take between 100,000 and 200,000 years．In the meantime,people could begin to live on the planet in special closed environments．They would provide a lot of useful information about conditions on the Mars and the problems connected with living there.The author's attitude towards the possibility of life on the Mars in the future is__.A.doubtfulB.positiveC.negativeD.uninterested
At the first sight the planet Mars does not appear very welcome to any kind of life．It has very little oxygen and water,the temperature at night is below-50~Cand winds of 100 miles per hour cause severe dust storms．However,the surface of the planet seems to show that water flowed across it some time in the past,and it is believed that there is enough ice at the poles to cover the planet with water if it melts．Although there is no life on the Mars now,some scientists think that there may have been some form of life long time ago．At that time,the planet had active volcanoes;the atmosphere was thicker and warmer;and there was water．In fact,in some ways the Mars may have been similar to the Earth,where life exists.
Some people believe that the Mars could support life in the future if the right conditions were produced．The first step would be to warm the planet using certain gases which trap the Sun's heat in the planet's atmosphere．With warmth,water and carbon dioxide(二氧化碳),simple plants could begin to grow．These plants could slowly make the Mars more suitable for living．It is estimated that the whole process might take between 100,000 and 200,000 years．In the meantime,people could begin to live on the planet in special closed environments．They would provide a lot of useful information about conditions on the Mars and the problems connected with living there.
The author's attitude towards the possibility of life on the Mars in the future is__.
Some people believe that the Mars could support life in the future if the right conditions were produced．The first step would be to warm the planet using certain gases which trap the Sun's heat in the planet's atmosphere．With warmth,water and carbon dioxide(二氧化碳),simple plants could begin to grow．These plants could slowly make the Mars more suitable for living．It is estimated that the whole process might take between 100,000 and 200,000 years．In the meantime,people could begin to live on the planet in special closed environments．They would provide a lot of useful information about conditions on the Mars and the problems connected with living there.
The author's attitude towards the possibility of life on the Mars in the future is__.
A.doubtful
B.positive
C.negative
D.uninterested
B.positive
C.negative
D.uninterested
参考解析
解析：根据全文可以判断，作者对人类在火星上生存的可能性抱着积极、乐观的态度。
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At the first sight the planet Mars does not appear very welcome to any kind of life．It has very little oxygen and water,the temperature at night is below-50~Cand winds of 100 miles per hour cause severe dust storms．However,the surface of the planet seems to show that water flowed across it some time in the past,and it is believed that there is enough ice at the poles to cover the planet with water if it melts．Although there is no life on the Mars now,some scientists think that there may have been some form of life long time ago．At that time,the planet had active volcanoes;the atmosphere was thicker and warmer;and there was water．In fact,in some ways the Mars may have been similar to the Earth,where life exists.Some people believe that the Mars could support life in the future if the right conditions were produced．The first step would be to warm the planet using certain gases which trap the Sun's heat in the planet's atmosphere．With warmth,water and carbon dioxide(二氧化碳),simple plants could begin to grow．These plants could slowly make the Mars more suitable for living．It is estimated that the whole process might take between 100,000 and 200,000 years．In the meantime,people could begin to live on the planet in special closed environments．They would provide a lot of useful information about conditions on the Mars and the problems connected with living there.Which is the best title for this passage?A.The Possibility of Life on the MarsB.Future Conditions on the MarsC.The Mars and the EarthD.A Study of the Climate of the Mars
At the first sight the planet Mars does not appear very welcome to any kind of life．It has very little oxygen and water,the temperature at night is below-50~Cand winds of 100 miles per hour cause severe dust storms．However,the surface of the planet seems to show that water flowed across it some time in the past,and it is believed that there is enough ice at the poles to cover the planet with water if it melts．Although there is no life on the Mars now,some scientists think that there may have been some form of life long time ago．At that time,the planet had active volcanoes;the atmosphere was thicker and warmer;and there was water．In fact,in some ways the Mars may have been similar to the Earth,where life exists.Some people believe that the Mars could support life in the future if the right conditions were produced．The first step would be to warm the planet using certain gases which trap the Sun's heat in the planet's atmosphere．With warmth,water and carbon dioxide(二氧化碳),simple plants could begin to grow．These plants could slowly make the Mars more suitable for living．It is estimated that the whole process might take between 100,000 and 200,000 years．In the meantime,people could begin to live on the planet in special closed environments．They would provide a lot of useful information about conditions on the Mars and the problems connected with living there.There could be life on the Mars in the future ifA.it supported life in the pastB.certain gases are used to cool the planetC.the atmosphere can be heated enough to grow simple plantsD.the planet's volcanoes become as active as they were in the past
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共用题干第一篇Water Resources on the EarthThe second most important constituent（构成成分）of the biosphere（生物圈）is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0℃and boils a 100℃．Life as we know it would only be possible on the surface of a planet which had temperature: somewhere within this narrow range.The earth's supply of water probably remains fairly constant in quantity.The total quantity of water is not known very accurately,but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers.Most of it is in the form of the salt water of the oceans一about 97 percent. The rest is fresh.But three-quarters of this is in the form of ice at the poles and or mountains and cannot be used by living systems until melted.Of the remaining fraction,which h somewhat less than one percent of the whole.There is 10—20 times as much stored underground water as there is actually on the surface.There is also a tiny,but extremely important fraction of the water supply which is present as water vapour in the atmosphere.Water vapour in the atmosphere is the channel through which the whole water circulation（循环） of the biosphere has to pass.Water evaporated（蒸发）from the surface of the oceans,from lakes and rivers and from moist（潮湿的）earth is added to it. From it the water comes out again as rain or snow,falling on either the sea or the land. There is,as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land,but there is more rainfall over the land than over the oceans and the balance is restored by the run off from the land in the form of rivers.The word"fraction"in the second paragraph means________.A:a large areaB:a very small amountC:an important systemD:a major source of information
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