The second most important constituent of the biosphere is liquidwater. This can only exist in a very narrow range oftemperatures,since water freezes at 0°C and boils at 100°C. Thisis only a tiny range compared with the low temperatures ofsome other planets and the hot interior of the earth, let thetemperature __1__of the sun.
As we know, life would only be possible on the face of a __2__planet had temperatures somewherewithin this range. __3__
The earth’s supply of water probably remains quite fairly constant __4__in quantity. A certainnumber 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 depthsof the __6__ earth during volcanic action. The total quantity of water is not known, and it is aboutenough to cover the surface of the globe __7__to a depth of about two and three-quarter kms.Most of it—97% is in the form of the salt waters of the oceans. The rest is fresh, but three quarterof this is in the form of ice at the Poles __8__ and on mountains, and cannot be used by livingsystems when __9__melted. Of the remaining fraction, which is somewhat fewer __10__than 1%of the whole, there is 10-20 times as much stored as underground water as is actually on thesurface. There is also a minor, but extremely important, fraction of the water supply which ispresent as water vapour in the atmosphere.
參考答案及解析:
1.Let ^the 加入alone. Let alone 意為“更不用說”， 表示一種讓步關系。
2.face-surface 根據(jù)上下文理解，應該指地球的表面。
3.planet^had 加入which或that。這樣使得planet后面的句子成為一個定語從句。
4.去掉fairly或quite 意思重復。
5.out改成outer 這里指外層空間。
6.去掉away rise后面不接away。
7.and改成although 短文中這里是讓步關系，而不是并列關系。
8.quarter改成quarters 英語表達中，當分子是二以上的數(shù)時，分母應為復數(shù)。
9.when改成until或者unless 根據(jù)上下文，這句話的意思應為:除非(冰雪)融化，否則(地球上的)生命系統(tǒng)就無法利用水。所以when在這里的意思有誤。
10.fewer改成less 文中的remaining fraction 仍指水，因此不能用fewer，要用less。