[填空题]

The second most important constituent of the biosphere is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0°C and boils at 100°C. This is only a tiny range compared with the low temperatures of some other planets and the hot interior of the earth, let the temperature（1）of the sun.
As we know, life would only be possible on the face of a（2）planet had temperatures somewhere within this range. （3）The earth’s supply of water probably remains quite fairly constant（4）in quantity. A certain number of hydrogen atoms, which are one of the main constituents of water, are lost by escaping from the atmosphere to out space, but they are probably just （5）about to be replaced by new water rising away from the depths of the （6）earth during volcanic action.
The total quantity of water is not known, and it is about enough to cover the surface of the globe （7）to a depth of about two and three-quarter kms. Most of it&mdash

[填空题]

The second most important constituent of the biosphere is liquid water. This can only exist in a very narrow range of temperatures,since water freezes at 0°C and boils at 100°C. This is only a tiny range compared with the low temperatures of some other planets and the hot interior of the earth, let the temperature（1）of the sun.
As we know, life would only be possible on the face of a（2）planet had temperatures somewhere within this range. （3）The earth’s supply of water probably remains quite fairly constant（4）in quantity. A certain number of hydrogen atoms, which are one of the main constituents of water, are lost by escaping from the atmosphere to out space, but they are probably just （5）about to be replaced by new water rising away from the depths of the （6）earth during volcanic action.
The total quantity of water is not known, and it is about enough to cover the surface of the globe （7）to a depth of about two and three-quarter kms. Most of it&mdash

[单项选择]Water
The second most important constituent(构成成份)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 at 100℃. Life as we know it would only be possible on the surface of a planet which had temperatures 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 -- about 97 percent. The rest is fresh,but three-quarters of this is in the form of ice at the Poles and on mountains, and cannot be used by living systems until melted. Of the remaining fraction, which is 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,
A. in the center of the earth.
B. on the surface of our planet.
C. in a very narrow range of temperatures.
D. in the coastal areas of the earth.

[简答题]　　　　　　　　　　　　　WATER The second most important constituent of the biosphere is liquid water. This can only exist in a very narrow range of temperatures, since water freezes at 0℃ and boils at 100℃. This is only a tiny range compared with the low temperatures of some other planets and the hot interior of the earth, let the temperature of the sun. 　　　　　　　　　　 (1)__________ As we know, life would only be possible on the face　　　　　　(2)__________ of a planet had temperatures somewhere within this range.　　　 (3)__________ The earth’’s supply of water probably remains quite fairly　　　 (4)__________ constant in quantity. A certain number of hydrogen atoms, which are one of the main constituents of water, are lost by escaping from the atmosphere to out space, but they are probably just about replaced by 　 　　 (5)__________ new water rising away from the depths of the earth during 　 　 (6)__________ volcanic action. The total quantity of water is not known, and it is about enough to cover