单选题
1.【阅读选择】The world is not only hungry;it is also thirsty for water. This may seem strange to you,since nearly 75% of the earth‘s surface is covered with water. But about 97% of this huge amount is sea-water,or salt water. Man can only drink and use the other 3%——the fresh water that comes from rivers,lakes,underground,and other sources. And we cannot even use all of that,because some of it is in the form of icebergs（冰山）and glaciers（冰川）.Even worse,some of it has been polluted.
What percentage of the earth‘s water can man actually use at present？
A.Nearly 75 per cent.
B.About 97 per cent.
C.Exactly 3 per cent.
D.Less than 3 percent.
正确答案：D
答案解析：根据本段得知，地球上只有3%的水适于人类饮用，然而部分以冰山或冰川的形式存在，还有的被污染，因而实际上人类能用的水要低于3%。