2.1 主要推展句

主要推展句(major supporting statement)的主要特點是：圍繞段落主題句展開的每一個推展句本身都不要求作進一步的說明或證明，句與句之間的關系是相互獨立又是互相連接的。

例1：(主題句) There are several factors affecting climate. (推展句1)One factor is the mount of sunlight received. (推展句2)Altitude, or the height above sea level, also determines climate. (推展句3)The oceans have an effect on the climate of adjacent land. (推展句4)In addition, climate is influenced by the general circulation of the atmosphere.

主題句指出影響氣候的幾個因素。然后用四個擴展句說明四種因素。第一種是太陽光的接收量，第二種是海拔高度，第三句和第四句分別是海洋和大氣環(huán)流因素。

2.2 次要推展句

次要推展句(minor supporting statement)是指對主要推展句作進一步的事實分析和舉例說明。它從屬于某一個或某幾個推展句。

例2：(主題句)I don't teach because teaching is easy for me. (主要推展句1)Teaching is the most difficult of the various ways I have attempted to earn my living: mechanic, carpenter, writer. (主要推展句2)For me, teaching is a red-eye, sweaty-palm, sinking-stomach profession. (次要推展句1)Red-eye, because I never feel ready to teach no matter how late I stay up preparing. (次要推展句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. (次要推展句3)Sinking-stomach, because I leave the classroom an hour later convinced that I was even more boring than usual.

從屬于主要推展句2的三個次要推展句起著解釋說明作用，分別解釋red-eye, sweaty-palm, sinking-stomach的含義，這就更加形象生動地證明了 "teaching is not easy" 這個主題。

2.3 主要推展句與次要推展句的關系

主要推展句與次要推展句的關系(relation)基本可以遵循下面的“三部分”(three-part)規(guī)則。

1〕每個主要推展句都應該是對主題句中表示主要思想的關鍵詞的直接、明確的說明。

2〕每個次要推展句都應該說明它的主要推展句。

3〕含有討論說明或分析的問題通常既要有主要推展素材，又要有次要推展素材。

2.4 寫好推展句的方法

主題句及關鍵詞確定后，開始選擇和主題有關的信息和素材。實質上，針對關鍵詞測試每一個所選擇的素材就是一個分類的過程。有一種常用的方法就是句子展開前加以設問，然后解答，即設問-解答(why-because)的方法。下面我們通過舉例來看一看這種分類過程是如何完成的。例3：

假設 (suppose) Topic sentence: English is an international language?

設問(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.

從上面可以看出，最初的三個推展句是和關鍵詞an international language一致的。第四句和主題句不統(tǒng)一，盡管第四句會成為另一主題句(Many Pakistanis speak English)很好的推展句。第五句說服力不強。

當然，在寫成段落時，沒有必要在每個句子開頭寫上 "because"，但是，在動筆展開句子時，頭腦里要想著這個詞，這種檢驗方法能幫助你把注意力集中在某個重心，圍繞主題思想層層展開。

上面我們討論了主要推展句的一種展開方法。而展開次要推展句的方法與主要推展句類似，這里我們就不再復述了。

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