It is widely believed that froth water will never be used up because we can get it from rain, rivers and wells.As a matter of fact, such belief is wrong and possibly dan gerous.

　　人们以为淡水是取之不尽的，因为我们可以从雨水、河水和井水中得到淡水。事实上，这种观点是错误的，很可能是危险的。