因果分析是常用的拓展段落的方法之一，一定要注意推理的逻辑性因果关系必须表达清楚，不能因果混淆，更不能因果倒置，要避免牵强附会和循环论证。一个原因可能造成一个或多个结果，也可能在一大段文章中涉及到一连串因果关系。一个结果也可能由多种原因所引起，通常先写结果，后写多种原因；但也可先写原因后写结果。另外，如果哟啊强调原因或结果，可用倒装或强调句型加以突出。「Example 」The surge of demand for oil will soon begin to send shock waves through the American economy and transportation system. The impact of these tremors can already be anticipated： to the consumer they signal the end of a long love affair with the car， and to Detroit they offer an early warning that its 1985 growth aims are dangerously unrealistic. Unless we exercise foresight and devise growth-limits policies for the auto industry， events will thrust us into a crisis that will lead to a substantial erosion of domestic oil supply as well as the independence it provides us with， and a level of petroleum imports that could cost as much as $20 to $30 billion per year. Moreover， we would still be depleting our remaining oil reserves at an unacceptable rate， and scrambling for petroleum substitutes， with enormous potential damage to the environment.

　　（七）定义法

　　有时候为了避免混淆或误解，我们必须对一个词、一条术语或谚语、一个概念通过下定义加以说明、解释。通常有三种方法下定定义：给出同义词、用一个带有定语从句的复合句或用一整段文章，而以第三种方法最为常用。1997 年1 月份四级考试的作文Practice Makes Perfect 就是一篇极为典型的定义型文章。「Example 」A “liberated woman” is simply a woman who controls her own life， rather than allowing it to be controlled by other people， traditions， or expectations. A “liberated woman” can be found pursuing any line of work， including housework， or no work at all. She may or may not be married； she may or may not have borne children. She may belong to any race； she may have attained any age. She need have only one trait in common with her “liberated sisters”： she makes her own choices， whether they be the colors on her walls or the advanced degrees she seeks. She acts of her own volition， responsible to herself， and not out of fear of what her mother， lover， or neighbor might say.

　　（八）分类法

　　所谓“分类”就是根据人物和事物的特征将他们/它们分别归入各自不同的范畴。在写这一类段落时，一定要抓住各个类别的典型特征，不要异类相串，混淆起来。「Example 」According to Xiao Li， the fifteen students of his class fall into three groups. Seven of them work hard and study well. They always get good marks in examinations and are often praised by the teachers. Li calls them “good students”。 The monitor， the secretary of the Youth League branch， and the captain of the class volleyball team， are quick in finding out what their fellow students are interested in or what they should do as a collective. They always organize proper activities at the proper time， so Li calls them “good organizers”。 Four other students are very kind to their classmates， always ready to lend them a helping hand. They help to clean the classroom and the corridor even when they are not on duty. Li says that they are “good fellows”。 “What about yourself？” someone asks him. “I'm a group by myself-a good observer.”

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