1. 主要拓展句

　　主要推展句（major supporting statement）主要特点是：围绕段落主题句展开每一个拓展句本身都不要求作进一步说明或证明，句与句之间关系是相互独立又是互相连接。

　　例1：（主题句）拓展句2）Altitude，or the height above sea level，also determines climate. （拓展句3）The oceans have an effect on the climate of adjacent land.（拓展句4）In addition，climate is influenced by the general circulation of the atmosphere.

　　主题句指出影响气候几个因素。然后用四个扩展句说明四种因素。第一种是太阳光接收量，第二种是海拔高度，第三句和第四句分别是海洋和大气环流因素。

2. 次要拓展句

　 次要拓展句（minor supporting statement）是指对主要拓展句作进一步事实分析和举例说明。它从属于某一个或某几个拓展句。

　　例2：（主题句）I don’t teach because teaching is easy for me.（主要拓展句1）Teaching is the most difficult of the various ways I have attempted to earn my living： mechanic，carpenter，writer.（主要拓展句2）For me，teaching is a red-eye，sweaty-palm，sinking-stomach profession.（次要拓展句1）Red-eye，because I never feel ready to teach no matter how late I stay up preparing.（次要拓展句2）Sweaty-palm，because I’m always nervous before I enter the classroom，sure that I will be found out for the fool that I am.（次要拓展句3）Sinking-stomach，because I leave the classroom an hour later convinced that I was even more boring than usual.

　　从属于主要拓展句2三个次要拓展句起着解释说明作用，分别解释red-eye，sweaty-palm，sinking-stomach含义，这就更加形象生动地证明了“teaching is not easy”这个主题。

　　3. 主要拓展句与次要拓展句关系

　　主要拓展句与次要拓展句关系（relation）基本可以遵循下面“三部分”（three-part）规则。

　　1）、每个主要拓展句都应该是对主题句中表示主要思想关键词直接、明确说明。

　　2）、每个次要拓展句都应该说明它主要拓展句。

　　3）、含有讨论说明或分析问题通常既要有主要拓展素材，又要有次要拓展素材。

　　4. 写好拓展句方法

　　主题句及关键词确定后，开始选择和主题有关信息和素材。实质上，针对关键词测试每一个所选择素材就是一个分类过程。有一种常用方法就是句子展开前加以设问，然后解答，即设问－解答（why-because）方法。下面我们通过举例来看一看这种分类过程是如何完成。例3：假设（suppose）Topic sentence： English is an international language? 设问（why）Why can we say English is an international language?

　　解答（because）Because：English is spoken by pilots and airport control operators on all the airways of the world.

　　Because：Over 70 percent of the world’s mail is written in English.

　　Because：More than 60 percent of the world’s radio programs are in English.

　　Because：Pakistan was once one of the British colonies.

　　Because：Many members of the International Language Society are selected from English-spoken countries.

　　从上面可以看出，最初三个拓展句是和关键词an international language一致。第四句和主题句不统一，尽管第四句会成为另一主题句（Many Pakistanis speak English）很好拓展句。第五句说服力不强。

　　当然，在写成段落时，没有必要在每个句子开头写上 “because”，但是，在动笔展开句子时，头脑里要想着这个词，这种检验方法能帮助你把注意力集中在某个重心，围绕主题思想层层展开。

补充阅读材料---拓展句

　段落发展手段及结尾段写法

　　在上一讲我们讲了主题句，推展句写法；这一讲我们要进一步来谈一谈段落发展几种手段以及结尾段写法。段落发展几种手段：

　　1、列举法（details）

　　作者运用列举法，是通过列举一系列论据对topic sentence中摆出论点进行广泛、全面地陈述或解释，列举顺序可以按照所列各点内容相对重要性、时间、空间等进行。

　　Yesterday as one of those fool days for me when everything I did went wrong. First，I didn’t hear my alarm clock and arrived late for work. Then，I didn’t read my diary properly and forgot to get to an important meeting with my boss. During the coffee break，I dropped my coffee cup and spoilt my neat skirt. At lunch time，I left my purse on a bus and lost all the money that as in it. After lunch，my boss as angry because I hadn’t gone to the meeting. Then I didn’t notice a sign on a door that said “wet Paint” and so I spoilt my jacket too. When I got home I couldn’t get into my flat because I had left my key in my office. So I broke into to get in but cut my hand.

　　根据本段主题句中关键词组everything I did went wrong，作者列举了8点内容，分别由first，then，during the coffee break，after lunch time等连接词语引出，使得该文条理清楚、脉络分明、内容连贯。常用于列举法过渡连接词有：for one thing ，for another，finally，besides，moreover，one another ，still another，first，second，also等。

　　2、举例法（example）

　　作者通过举出具体事例来阐述、说明主题句内容，严格地讲，举例法也是列举法一种，它们区别在于：列举法侧重罗列事实，所列事实力求全面；而举例法侧重通过举出典型事例来解释作者观点，且事例可多可少。我们来看下面这个用举例法展开段落。

　　There are many different forms of exercises to suit different tastes. For example，those ho enjoy competitive sports may take up ball games. For another example，if they prefer to exercise alone，they can have a run or take a walk in the morning or in the evening. Besides，people can go swimming in the summer and go skating in the inter. In short，no matter hat their interests are，people can always find more than one sports that are suitable to them.

　　本段采用了三个事例来说明主题句中关键词组different forms of exercises，这三个例子分别由连接词for example，for another example 和 besides引出，最后由引导结尾句总结全段内容。举例法中常用连接词有：for example（instance），one example is，besides，furthermore，moreover，in addition等。

　　3、叙述法（narration）

　　叙述法发展段落主要是按照事物本身时间或空间排列顺序，通过对一些特有过渡连接词使用，有层次分步骤地表达主题句一种写作手段。用这种方法展开段落，作者能够清楚连贯地交待事物本末，从而可以使读者可以清晰、完整地理解文章含义，例如：

　　In the flat opposite，a woman heard the noise outside. hen she looked out through the indo，she discovered that her neighbor as threatened by someone. She immediately called the police station. In answer to the call，a patrol police car arrived at the scene of the crime quickly. Three policemen went inside the flat at once，and others guarded outside the building to prevent anyone from escaping.

　　这段是按照事物发展先后顺序，叙述从发现案情、报警、到警察赶到、包围现场过程。全文脉络清晰，叙述层次感强，结构紧凑。常用于叙述法中过渡连接词有：first，an the beginning，to start with，after that，later，then，afterwards，in the end，finally等。

　　4、对比法或比较法（comparison & contrast）

　　将同类事物按照某种特定规则进行比较分析是一种常用思维方法。通过对比，更容易阐述所述对象之间异同和优缺点，例如：

　　The heart of an electronic computer lies in its vacuum tubes，or transistors. Its electronic circuits work a thousand times faster than the nicer cells in the human brain. A problem that might take a human being a long time to solve can be solved by a computer in one minute.

　　在这段文字上，作者为了突出电子计算机运行速度之快，首先将它与人脑进行了比较，“—— a thousand times faster than ——”；而后，又将这一概念具体到了“a problem”上，通过对比使读者从“—— a long time —— in one minute”上有更加直观认识。

　　常用于对本法或比较法上过渡连接词有：than，compared with等。

　　5、分类法（classification）

　　在阐述某一概念段落中，常用分类法。通过对概念中所包括事物进行分门别类，分别加以叙述，使读者有更为清晰认识，如：

　　Ever since humans have lived on the earth，they have made use of various forms of communication. Generally，this expression of thoughts and feelings has been in the form of oral speech. hen there is a language barrier，communication is accomplished through sign language in which motions stand for letters，words and ideas. Tourists and the people unable to hear or speak have had to resort to this form of expression. Many of these symbols of hole words are very vivid and exact and can be used internationally；spelling，whoever，cannot. Body language transmits ideas or thoughts by certain actions，either intentionally or unintentionally. A nod signifies approval，while shaking the head indicates a negative reaction. Other forms of nonlinguistic language can be found in signal flags，Morse code，and picture signs.

　　在该段中为了说明topic sentence中“various forms of communication”，作者将其分为oral speech，sign language，body language及other forms of nonlinguistic language，并逐加阐述。

　　采用这种方法段落并没有标志突出连接词，所述各项均为平行并列关系，所以没有明显主次之分。

　　6、因果分析法（cause and effect）

　　在阐述某一现象段落中，常采用因果分析法。例如：

　　The role of omen in today’s society is changing. One reason is that women have begun to assert themselves as independent people through the omen’s movement. Also，omen are aware of the alternatives to staying at home. Another reason is that increasing numbers of omen ho enter ne fields and interests serve as role models for other omen. Moreover，men are becoming more conscious of the abilities of omen and have begun to vie their independence positively.

　　本段中，主题句提出了一种社会现象，推展句则对产生这种现象原因作出各种解释。常用于因果分析法连接词有：because，so，as a result等。

　　7、定义法（definition）

　　在科普文章写作中，定义法是必不可少。通过下定义，可以使读者对该事物有一个更直接认识。

　　Automation refers to the introduction of electronic control and automation operation of productive machinery. It reduces the human factors，mental and physical，in production，and is designed to make possible the manufacture of more goods with fewer workers. The development of automation in American industry has been called the “Second Industrial Revolution”。

　　这一段文字使我们了解了“automation”和“Second Industrial Revolution”两个概念，分别由“refers to”和“been called”引出。常出现在定义法中词语有：refer to，mean，call等。

　　8、重复法（repetition）

　　句子一部分反复出现在段落中，这就是重复法。它往往造成一种步步紧逼气氛，使文章结构紧凑，有感染力。比如：

　　Since that time，which is far enough away from no，I have often thought that few people know hat secrecy there is in the young，under terror. I as in mortal terror of the young man ho anted my heart and liver；I as in mortal terror of my interlocutor with the iron leg；I as in mortal terror of myself，from whom an awful promise had been extracted；

　　该段中反复应用了I as in mortal terror of …我经常处于恐怖之中。以上，我们结合具体文章讨论了展开段落几种方法。在实际写作中，我们往往不必拘泥于一种写作方法，而是将若干方法穿插在一起，使文章有声有色。