解释说明类作文
解释说明文用于解释一种社会现象或—个问题，题目中常常会提供实例图表。对于这类文章应先用引言引出需要解释的现象或问题，写出主题句;其次.指出造成这一现象或问题的原因.并用拓展句对此加以具体说明;最后，提出解决问题的方法、展望或建议。
提纲：观点——分析——结论
真题：Global Shortage of Fresh Water(1996年6月题)
Directions：For this part，you are allowed thirty minutes to write a composition On the topic“Global Shortage Of Fresh Water'’.You should write at least 100 words and you should base your composition On the outline (given in Chinese) below.
Outline：1.人们以为淡水是取之不尽的(提示：雨水，河水，井水……)。
2.实际上淡水是非常紧缺的(提示：人口增长、工业用水增加，污染……)。
3.我们该怎么办。
审题：问答式：问：Why is there a shortage of fresh water?
答：Many people believe that fresh water is inexhaustible.
拟提纲：
观点：Our fresh water is far from adequate.
分析：There are three reasons：
a.Population growth.
b.An increasing amount of water used i industry.
c.Fresh water resources are polluted by factories.
结论：Take measures to solve the problem.
a.To control the population.
b.To build water treatment plant.
c.To save water.
范文1;
Many people believe that the supply of fresh water on the earth is inexhaustible(用现象表述引出人们普遍的想法和原因)because they can get fresh water from the tap in their kitchen and see it from rain，rivers or lakes.Unfortunately，this belief is wrong (过渡句，为下一段中心思想的出现做铺垫).
Study shows that our freshwater is far from adequate(以科学反驳人们的错误想法，并确定中心思想).Generally，there are three major reasons(具体说明其原因)：first，with the increase in the world's population，a call for fresh water is growing gradually;second，with the rapid development of industry，an increasing amount of water is needed;to make things worse，fresh water resources are polluted by most factories and liquid waste of daily life.If such situation keeps going On，it will be dangerous(过渡句).
In this case，it is important for us to take measures to solve the problem.Governments Of many countries should control the population.Water treatment plants should be built to protect water resources from being polluted.What's the most important，people should be aware of the great necessity of saving water. (提出解决问题的方法，与第二段的原因一一对应。)