1. 人们认为淡水是取之不尽的(提示：雨水，河水，井水)

2. 实际上淡水是短缺的(提示：人口增加，工业用水增加，污染严重)

3. 我们应当怎么办(提示：节约用水，开发新水源)

例文： Global Shortage of Fresh Water

People often think that water will never be used up. There is plenty of water, such as rain, water from the rivers and wells. It seems as if water is always available What should we do about the shorage? I first, the people should save on water and certain law no water will be polluted. We have to protect the new ones. In this way I believe