单选题_____ from space, our earth, with water covering 70% of its surface, appears as a “blue planet”.A SeeingB To be seenC SeenD Having seen
题目
单选题
_____ from space, our earth, with water covering 70% of its surface, appears as a “blue planet”.
A
Seeing
B
To be seen
C
Seen
D
Having seen
相似考题
更多“单选题_____ from space, our earth, with water covering 70% of its surface, appears as a “blue planet”.A SeeingB To be seenC SeenD Having seen”相关问题
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第1题：
Passage Three
Many theories about the origin of the ocean have been proposed by scientists. The most widely accepted one is that the earth at some time in its very early history became hot enough to melt the materials from which it was formed. While in this molten state, lighter rock-forming materials (造岩材料) floated on the surface of the heavier ones. Then, between four and a half four billion (十亿) years ago, the molten earth cooled sufficiently to form. a crust of rock that was many miles thick.
Surrounding the earth was an unbroken canopy of clouds miles thick and made up mostly of water vapor. Rain falling toward the still-hot earth was heated to steam and rose to the clouds again. After many millions of years, as the earth continued to cool, its surface temperature fell below the boiling point of water. Rainwater could now remain on the earth, covering its whole surface except for the higher places on earth that had been formed from the lighter rock materials.
In 1970, scientists had pieced together evidence that the lighter rock materials had formed one huge continent by a vast ocean. Then, about 200 million years ago, the great continent began to break up, the pieces moving slowly apart.
The onrushing waters of the single huge ocean now entered and filled the spaces between the separating continents--and became the several oceans and seas we know today.
41. This passage mainly talks about ______.
A. the origin of the earth
B. the origin of the ocean
C. the history of the earth
D. the forming of the earth's crust
正确答案：B41．答案为B。根据第一段第一、二句，Many theories about the origin of the ocean have been proposed by scientists．The most widely accepted one is that...作出该项选择。
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第2题：
( ) from the moon, our earth, with water ( ) seventy percent of its surface, appears as a “blue ball”.A. Seen…covered
B.Seeing…covering
C.Seen…covering
D.To see…to cover
参考答案：C
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第3题：
The old couple () good times and hard times as well.A、has seen
B、had seen
C、have seen
D、having seen
参考答案：C
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第4题：
_________ from space, the earth looks like a blue ball.
A、Seeing
B、Seen
C、To see
D、See
参考答案：B
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第5题：
_____ from the hill , we find the scenery very beautiful.A. Seeing
B. To see
C. Seen
D. Saw
正确答案：A
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第6题：
Passage 2
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 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 atmosphere
B. its atmosphere is the same as the earth's
C. there is a good supply of water on Venus
D. the days on Venus are long enough答案：A解析：由第二段第一句中的“itwill be possible to change the atmosphere ofVenus and so create a new worl d”可知.so是表示因果的连接词，前因后果，所以正确答案A。 -
第7题：
共用题干
第一篇
Water Resources on the Earth
The 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.Most of the fresh water on Earth________.
A:is in the form of ice at the poles and on mountains
B:is stored underground
C:is found in rivers and lakes
D:comes from the rain答案：A解析：文章第一段的第二句讲到液态水“only exist in a very narrow range of temperatures"，虽然B（我们星球的表面）也有点道理，但是液态水对温度的要求很高，并非地球的所有表面都有液态水存在，所以答案D正确。
第二段第一句提到地球上水的供给“remains fairly constant in quantity"，数量上是恒定的，它就没有增加也不会减少，只不过会以不同的形态出现，所以选择B（保持不变）。
问题是“地球上绝大部分淡水以什么形式出现？”第二段中间提到淡水时，说到“three-quarters of this is in the form of ice at the poles and on mountains"，即3/4的淡水以冰的形式存在于两极和高山中，后面提到剩余部分的淡水存在于地下，但占比少于1%,所以选项A正确。
词义辫析题， fraction有“小部分”的意思，考虑到前面提到地球97％的水以海洋咸水的形式存在，剩下的3％则以冰的形式存在于两极和高山，余下的自然不多，所以选B。
第三段的最后一句说到“there is more rainfall over the land than over the oceans”，陆地的降雨比海洋要多，但没有提到河流和山脉的降雨比较，所以C正确。大气中的水蒸气是整个生物圈的水循环必经的途径。水从海洋的表面、湖泊、河流和潮湿的泥土中蒸发出来并补充到大气中。水以雨或雪的形式再次出现，降落在海洋或陆地上。可以预料到的是，海洋上空每单位面积的水蒸气比在陆地上空更为密集，但是，陆地比海洋有更多的降雨，水在陆地上以河流的形式流出以保持水资源的平衡。 -
第8题：
共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.According to the passage,"weight"should be understood in the sense that
A:it is fixed if it is outside the earth's gravitational puli
B:it decreases four times when it is 4,000 miles from the earth's center
C:it varies with the change of the gravitational attraction between two objects
D:things increase in amount as they are closer to the earth's surface答案：C解析：第一段最后一句表明，1磅重的黄油在离地球表面4000英里处重达0.25磅，第二段第一句也表明在4000英里高空处的物体重量仅为其在地球表面的重量的1/4。由此可推算出，4磅重的茶叶在离地球表面4000英里处重达1磅。
第一段第一句表明，我们之所以不能打破固有思维，是因为我们已经习惯了地球上的生活，也就是说，我们正是因为太过熟悉地球上的事物，才没有去质疑这些固有思维。
第一段第二句表明，物体的重量并非固定不变。第二段解释说，物体的重量源于物体间的引力。也就是说，物体的重量随着物体间引力的改变而改变。
最后一段第三句说明一个物体产生的引力与物体本身的重量有关。最后一段第四句又表明由于本身重量较小，一包黄油产生的引力很有限，相对于月球、地球、太阳等产生的强劲引力来说，比较容易被我们忽略。
本篇文章通篇讲的是重量是由引力产生的，并进一步阐述了物体间引力的变化、物体本身的重量，以及物体间的距离这三者之间的关系，主要讲的还是引力对重量的作用。 -
第9题：
共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.We do not feel the gravitational pull of a packet of butter because
A:it is too small to have a gravitational pull of its own
B:its puil is so small that we tend to ignore it
C:its pui1 disappears in the presence of the earth's gravitation
D:it tends to melt and loses its gravitational puli答案：B解析：第一段最后一句表明，1磅重的黄油在离地球表面4000英里处重达0.25磅，第二段第一句也表明在4000英里高空处的物体重量仅为其在地球表面的重量的1/4。由此可推算出，4磅重的茶叶在离地球表面4000英里处重达1磅。
第一段第一句表明，我们之所以不能打破固有思维，是因为我们已经习惯了地球上的生活，也就是说，我们正是因为太过熟悉地球上的事物，才没有去质疑这些固有思维。
第一段第二句表明，物体的重量并非固定不变。第二段解释说，物体的重量源于物体间的引力。也就是说，物体的重量随着物体间引力的改变而改变。
最后一段第三句说明一个物体产生的引力与物体本身的重量有关。最后一段第四句又表明由于本身重量较小，一包黄油产生的引力很有限，相对于月球、地球、太阳等产生的强劲引力来说，比较容易被我们忽略。
本篇文章通篇讲的是重量是由引力产生的，并进一步阐述了物体间引力的变化、物体本身的重量，以及物体间的距离这三者之间的关系，主要讲的还是引力对重量的作用。 -
第10题：
共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.We find it hard to break free from ideas connected with living on the earth because______.
A:it demands too great an effort for us to do so
B:we are too familiar with the way things are to question the ideas
C:we have proved that those ideas are correct
D:we are so sure of ourselves that we never doubt anything on the earth答案：B解析：第一段最后一句表明，1磅重的黄油在离地球表面4000英里处重达0.25磅，第二段第一句也表明在4000英里高空处的物体重量仅为其在地球表面的重量的1/4。由此可推算出，4磅重的茶叶在离地球表面4000英里处重达1磅。
第一段第一句表明，我们之所以不能打破固有思维，是因为我们已经习惯了地球上的生活，也就是说，我们正是因为太过熟悉地球上的事物，才没有去质疑这些固有思维。
第一段第二句表明，物体的重量并非固定不变。第二段解释说，物体的重量源于物体间的引力。也就是说，物体的重量随着物体间引力的改变而改变。
最后一段第三句说明一个物体产生的引力与物体本身的重量有关。最后一段第四句又表明由于本身重量较小，一包黄油产生的引力很有限，相对于月球、地球、太阳等产生的强劲引力来说，比较容易被我们忽略。
本篇文章通篇讲的是重量是由引力产生的，并进一步阐述了物体间引力的变化、物体本身的重量，以及物体间的距离这三者之间的关系，主要讲的还是引力对重量的作用。 -
第11题：
单选题The best title for this passage is _____.ATraveling in Space
BSleeping in the Spacecraft.
CEquipment Used by Astronauts.
DThe Earth Seen from Outer Space.
正确答案： D解析：
主旨归纳题。文章一开始提到飞船中没有床，而是用睡袋睡觉，在第二、三段中说明了在飞船中的睡眠时间，文章的最后介绍了宇航员睡觉的姿势和自己睡觉的偏好和习惯，因此可以断定文章主要说的是在宇宙飞船中是如如何睡觉的。故正确答案为B。A、C、D项都是以偏概全，说法过于片面。 -
第12题：
单选题_____ from space, our earth, with water covering 70% of its surface, appears as a “blue planet”.ASeeing
BTo be seen
CSeen
DHaving seen
正确答案： C解析：
句意：从太空看，我们的地球表面70%都被水覆盖，看起来像是一个“蓝色的星球”。本题考查非谓语动词用法。主语our earth与see之间是被动关系，应填入过去分词作状语，表示被动意义。因此C项正确。 -
第13题：
It can be learned from the passage that about four billion years ago ______.
A. the earth was in molten state
B. the earth surface temperature was above 100℃
C. the earth surface temperature was below 100℃
D. rain water could remain on the earth
正确答案：B43．答案为B。根据第一段最后一句及第二段内容可知，雨水在地表温度降到水的沸点以下才能停在地表，由此可知大约在四十亿年前，地表温度应在沸点以上。
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第14题：
( ) the house on fire, he dialed 91A、Seen
B、Seeing
C、Having been seen
D、Being seen
参考答案：B
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第15题：
The weight of an object in space is not the same ______ its weight on the surface of the earth.A.that
B.as
C.which
D. then
参考答案:B
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第16题：
If Tony ( ) that late film last night, he wouldn’t be so sleepy.A、didn’t see
B、haven’t seen
C、wouldn’t have seen
D、hadn’t seen
参考答案：D
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第17题：
--Have your students ever seen the silent film?
--No, they are too young ______ the old film.
A. to seeing
B. have seen
C.to have seen
D. to have
正确答案：C答案为C。“你的学生们看过无声电影吗？”“没有，他们太年轻了，没有看过老电影。”不定式的完成式表示不定式的动作发生在谓语动词之前。只有C形式正确。
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第18题：
Passage 2
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 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 atmosphere
B．its atmosphere is the same as the earth's
C．there is a good supply of water on Venus
D．the days on Venus are long enough答案：A解析：由第二段第一句中的“itwill be possible to change the atmosphere ofVenus and so create a new worl d”可知．so是表示因果的连接词，前因后果，所以正确答案A。 -
第19题：
共用题干
第一篇
Water Resources on the Earth
The 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.Liquid water only exists________.
A: in the center of the earth
B:on the surface of our planet
C:in the coastal areas of the earth
D:in a very narrow range of temperatures答案：D解析：文章第一段的第二句讲到液态水“only exist in a very narrow range of temperatures"，虽然B（我们星球的表面）也有点道理，但是液态水对温度的要求很高，并非地球的所有表面都有液态水存在，所以答案D正确。
第二段第一句提到地球上水的供给“remains fairly constant in quantity"，数量上是恒定的，它就没有增加也不会减少，只不过会以不同的形态出现，所以选择B（保持不变）。
问题是“地球上绝大部分淡水以什么形式出现？”第二段中间提到淡水时，说到“three-quarters of this is in the form of ice at the poles and on mountains"，即3/4的淡水以冰的形式存在于两极和高山中，后面提到剩余部分的淡水存在于地下，但占比少于1%,所以选项A正确。
词义辫析题， fraction有“小部分”的意思，考虑到前面提到地球97％的水以海洋咸水的形式存在，剩下的3％则以冰的形式存在于两极和高山，余下的自然不多，所以选B。
第三段的最后一句说到“there is more rainfall over the land than over the oceans”，陆地的降雨比海洋要多，但没有提到河流和山脉的降雨比较，所以C正确。大气中的水蒸气是整个生物圈的水循环必经的途径。水从海洋的表面、湖泊、河流和潮湿的泥土中蒸发出来并补充到大气中。水以雨或雪的形式再次出现，降落在海洋或陆地上。可以预料到的是，海洋上空每单位面积的水蒸气比在陆地上空更为密集，但是，陆地比海洋有更多的降雨，水在陆地上以河流的形式流出以保持水资源的平衡。 -
第20题：
共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.How much would four pounds of tea weigh if it was taken 4,000 miles out from the surface of the earth?
A:1 pound.
B:2 pounds.
C:3 pounds.
D:4 pounds.答案：A解析：第一段最后一句表明，1磅重的黄油在离地球表面4000英里处重达0.25磅，第二段第一句也表明在4000英里高空处的物体重量仅为其在地球表面的重量的1/4。由此可推算出，4磅重的茶叶在离地球表面4000英里处重达1磅。
第一段第一句表明，我们之所以不能打破固有思维，是因为我们已经习惯了地球上的生活，也就是说，我们正是因为太过熟悉地球上的事物，才没有去质疑这些固有思维。
第一段第二句表明，物体的重量并非固定不变。第二段解释说，物体的重量源于物体间的引力。也就是说，物体的重量随着物体间引力的改变而改变。
最后一段第三句说明一个物体产生的引力与物体本身的重量有关。最后一段第四句又表明由于本身重量较小，一包黄油产生的引力很有限，相对于月球、地球、太阳等产生的强劲引力来说，比较容易被我们忽略。
本篇文章通篇讲的是重量是由引力产生的，并进一步阐述了物体间引力的变化、物体本身的重量，以及物体间的距离这三者之间的关系，主要讲的还是引力对重量的作用。 -
第21题：
共用题干
Where Did the Earth's Water Come From?
Earth is located within the"snow line"of the solar system,the region closest to the Sun where H2 0 is primarily in liquid or gaseous form,if at all.______(46)The snow line phenomena is reflected in the water content of planets like Mercury,Venus,and Mars. Water is absent on Mercury.On Venus,H2O only exists as a trace element in the atmosphere.Mars only has a thin veneer of ice in its polar regions.In general,water is rare within the snow line.
Why does Earth have so much water relative to the other inner planets?71%of the surface is covered in the oceans,more than half of which is deeper than 3,000 meters,with an approximate total volume of 1.3 billion cu km.______(47)
There are various theories as to where all the Earth's water came from,but several theories have fared better than the others.______(48)When the Earth was in the process of forming,with a radius just 40%smaller than at present,it would have had enough gravity to hold on to a tenuous atmosphere with water vapor. The first water vapor on the planet would have come from the planet's internals,where volatile(low weight)chemicals would have a tendency to float to the top,and heavy chemicals(iron and nickel)would sink.
Though the first of Earth's water came about through volcanism,this alone probably didn't produce enough to form stable pools on the surface.______(49)Comparing the isotope ratios of water on Earth and water from comets and asteroids has revealed that the majority of the Earth's water comes from asteroids.
Throughout its history,Earth's water has increased in volume due to biological processes. In the early seas of Earth,hydrogen sulfide would have been in great supply,which,when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria,would have produced hydrogen,sulfur,and water.______(50)________（49）
A: More water was added to the planet during several hypothesized large impacts from asteroids from the outer asteroid belt.
B:We know that the oceans existed as early as 100 million years after the formation of the Earth.
C:Still,the oceans only make up 0.023%of the Earth's total mass.
D:Astronomers say Earth s water may have come from space.
E:The snow line is located in the outerasteroid belt,between the orbits of Mars and Jupiter.
F: Many geologists believe that the majority of Earth's water generated through this process.答案：A解析：文中第一段第一句提到了snow line，接下来的依据肯定还是要对snow line进行进一步说明，而选项中，只有E选项提到了snow line，所以选择E。
文中第二段主要说明地球上的水占的比重，而只有C选项是对这一主题进行说明，所以选择C。
根据后一句When the Earth was in the process of forming可以得知，该段是在讲述地球的形成历史，B选项We know that the oceans existed as early as 100 million years after the formation of the Earth也是在讲述地球形成的历史，所以选择B。
后一句：Comparing the isotope ratios of water on Earth and water from comets and asteroids has revealed that the majority of the Earth's water comes from asteroids．通过把地球上水的同位素和小行星以及彗星上的水的同位素进行比较，发现地球上的水主要来自小行星。可以推断出，该句要讲述地球上的水与太空中小行星的关系，所以A选项正确。
文中的最后一段主要是讲地球上水的来源。前一句：In the early seas of Earth,hydrogen sulfide would have been in great supply,which,when reacted with carbon dioxide from the atmosphere during photosynthesis in sulfide-reducing bacteria,would have produced hydrogen , sulfur , and water．在地球早期的海洋中，硫氢化合物非常丰富，在去硫细菌的光合作用的影响下，它与大气层中的二氧化碳产生化学反应，产生大量的氢、硫，以及水。这是地球自身产生的水，而F选项Many geologists believe that the majority of Earth's water generated through this process(许多地理学家认为地球上水的产生主要通过这一进程实现）正好承接前一句，所以F选项正确。 -
第22题：
共用题干
Weight on and off the Earth We are so used to.our life on the surface of the earth that it can be quite an effort for our mind to break free of all the ideas that we take for granted.Because we can feel that things are heavy,we think of "weight"as being a fixed quality in an object,but it is not really fixed at all.If you could take a one-pound packet of butter 4,000 miles out from the earth,it would weigh only a quarter of a pound. Why would things weigh only a quarter as much as they do at the surface of the earth if we took them 4,000 miles out into space?The reason is this:all objects have a natural attraction for all other objects;this is called gravitational attraction.But this power of attraction between two obects gets weaker as they get farther apart.When the butter was at the surface of the earth,it was 4,000 miles from the center.When we took the butter 4,000 miles out,it was 8,000 miles from the center,which is twice the distance.If you double the distance between two objects,their gravitational attraction decreases two times two.If you treble the distance, it gets nine times weaker(three times three)and so on. So this is one of the first things we need to remember that the weight of an object in space is not the same as its weight on the surface of the earth. What about the weight of our pound of butter on the surface of the moon?At the distance the puii of the earth is about 4,000 times smaller than it is here on the surface,so we can forget all about the earth-pull on our butter. On the other hand,on the moon there will be an attraction between the butter and the moon,but the butter will weigh only about one-sixth as much as it does on the earth.This is because the moon is so much smaller than the earth.The amount of gravitational pull that a body produces depends on the amount of material in it.A packet of butter has a gravitational pull of its own;but this is very small in relation to the pull of something as large as the moon,or the earth,or the sun.The main idea of this passage is
A:different weight systems in different places
B:freedom from traditional ideas
C:traveling from the earth to the moon
D:the effect of gravitation on weight答案：D解析：第一段最后一句表明，1磅重的黄油在离地球表面4000英里处重达0.25磅，第二段第一句也表明在4000英里高空处的物体重量仅为其在地球表面的重量的1/4。由此可推算出，4磅重的茶叶在离地球表面4000英里处重达1磅。
第一段第一句表明，我们之所以不能打破固有思维，是因为我们已经习惯了地球上的生活，也就是说，我们正是因为太过熟悉地球上的事物，才没有去质疑这些固有思维。
第一段第二句表明，物体的重量并非固定不变。第二段解释说，物体的重量源于物体间的引力。也就是说，物体的重量随着物体间引力的改变而改变。
最后一段第三句说明一个物体产生的引力与物体本身的重量有关。最后一段第四句又表明由于本身重量较小，一包黄油产生的引力很有限，相对于月球、地球、太阳等产生的强劲引力来说，比较容易被我们忽略。
本篇文章通篇讲的是重量是由引力产生的，并进一步阐述了物体间引力的变化、物体本身的重量，以及物体间的距离这三者之间的关系，主要讲的还是引力对重量的作用。 -
第23题：
单选题As observed from the Earth，the angle between lines from the Earth to the Sun and the Earth to an inferior planet is known as（）.Aelongation
Bconjunction
Copposition
Dquadrature
正确答案： A解析： 暂无解析 -
第24题：
单选题_____from space, our earth, with water covering 70% of its surface, appears as a blue planet.ASeeing
BTo be seen
CSeen
DHaving seen
正确答案： C解析：