在前幾單元中，我們談到寫段落的第一個步驟是寫主題句。作者要對主題句在某些方面加以限制。第二個步驟將是寫推展句。例如你要陳述你選擇某院校的'理由，第一步，寫出主題句：
There are two main reasons why I have decided to attend Bingston University next year.
第二步，以數個理由推展你的主題：
示範段落4-1
① There are two main reasons why I have decided to attend Bingston University next year.② First of all， there is the question of money：Bingstonvs tuition is reasonable and I dont even have to pay it all at once.③ This is very important， since my father is not a rich man.④ With Bingstons deferred payment plan， my father will be able to pay my tuition without too much difficulty.⑤The second resaon is the fine education which I feed will receive there in agriculture， my chosen field.⑥ It is a well-known fact that Bingston hires only the finest professors in its Agriculture Department.⑦ Moreover， the university reqires all agricultural students to get practical experience by working on farms in the areawhile they are still going to school.
4.2示範段落分析
細節： two main reasons：
理由 1financial consideration②
a. reasonable tuition③
