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导语：以下英语网为大家整理了全面的职称英语考试历年真题及答案解析，《职称英语考试试题汇总：历年真题及答案解析》供大家参考学习。更多职称英语考试试题敬请关注英语网！ 【推荐】关注英语网微信：yingyuwang2013，更快获取真题答案及成绩查询信息。 第4部分：阅读理解（第31～45题，每题3分，共45分） 下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。 第一篇 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 earths 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 per cent. 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 fractional which is somewhat less than one per cent 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 vapor in the atmosphere. | 
