(5)比较和对比 比较(comparison)主要是指出两个或两个以上不同种类的事物的共同点或相似之处，如人物、地点、事物、思想、观点等。对照(contrast)主要是指出它们的不同点。相同的或类似的特征可以组成比较，不同的特征则可以组成对照。不仅如此，比较和对比常常同时使用，这是因为比较中往往隐含着对比。
比较和对比常有两种形式，即整体比较和对比(block comparison and contrast)与逐项比较(alternating comparison)，例如：
Although Ulysses S. Grant and Robert E. Lee were fierce adversaries during the Civil War, their lives, both military and nonmilitary, has a great deal in common. Grant descended from a family whose members participated in the American Revolution. He received his commission of second lieutenant from West Point and served in the Spanish-American War. He was later summoned by President Lincoln to assume command of the Union Forces during the Civil War. After the Civil War, Grant suffered financial problems and was forced to declare bankruptcy. Lee also descended from a family which engaged in the American Revolution. He, too, received his commission from West Point and later fought in Mexico during the Spanish-American War. His fame as a military strategist during the Civil War, when he was the commander of the Confederate armies, is well known. Although it is not always pointed out by historians he, like Grant, had financial difficulties after the civil War and was compelled to declare bankruptcy. By securing a post as president of Washington College, he was able to avoid additional poverty.(整体比较)
The same qualities that make people good houseguests make them good hospital patients. Good houseguests can expect a reasonable amount of service and effort on their behalf, and hospital patients can also. Guests have to adjust to what is for them a change, and certainly hospital patients must do the same. No one appreciates a complaining, unpleasant, unappreciative house guest, and the hospital staff is no exception. Hose guests who expect vast changes to be made for their benefit are not popular for long. Certainly nurses and other personnel with their routines feel the same way about patients in their care. Just as house guests must make adjustments to enjoy their visits, so patients must make adjustments to make their stays reasonably pleasant and satisfying under the circumstances.(逐项比较)
(6)原因和结果 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。例如：
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.
(7)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。再看下面的例子：
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 born 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.
