【正确答案】
People tend to think that there is enough fresh water for us to use. But as a matter of fact, fresh water is becoming scarce in many places of the world.
The problem of water shortage is caused by two factors. One is that the population is increasing fast, and the other is that many rivers have been polluted seriously.
Many ways can be used to solve this serious problem,but the following ones may be more effective.
First of all, we must take actions to fight against water pollution. Besides, we should practice birth control. Another way is to use better ways to irrigate the land. Finally we should never waste any water in our daily life.
Maybe these are not the best or only measures we can take. But it should be noted that we should take strong actions to make use of every drop of water. Only in this way can the problem be solved.

【答案解析】[解析] 本文的主题是“如何解决水资源短缺问题”，因此首段可以谈及人们以为淡水是取之不尽的，实际上淡水资源十分有限，然后分析造成这种现象的原因。在随后的段落可以列举解决问题的各种方法，最后作出总结。