单选题
[阅读选择]But even if every large city purified and reused its water， we still would not have enough. Where could we turn next？ To the oceans！ All we‘d have to do to make use of the vast amount of sea-water is —— remove the salt. This salt-removing process is already in use in many parts of the world.
According to the passage， sea-water can be turned into fresh water by_____
A.heating it up.
B.treating it with chemicals.
C.taking salt out of it.
D.drying it up.
正确答案：C
答案解析：海水之所以不能饮用就是因为它是咸的。答题依据是本段的remove the salt即take salt out。