Public opinions on what it takes to succeed in ones studies or career vary widely. Given approximately equal circumstances， some claim the success factor is largely a matter of luck—being in the right place and the right time. Others speak of utter devotion to work， combined with a degree of ruthlessness. Still others maintain that it is undoubtedly a matter of how much intelligence you have or simply how much education your mother had. In a word， people have different ideas on it.
本段的主题句Public opinions on what it takes to succeed in ones studies or career vary widely.放在段落的开头，开门见山地点明主题，使读者很容易抓住本段的写作主线：对学业或事业成功所持的各种不同的观点和看法。
The purpose of this book is to provide you with practice in spelling English. It is not a book that treats the complex rules of English orthography. Neither does it teach you how to use a dictionary. Its main objective is to introduce regular spelling patterns： that is， to present a regular system for spelling a large group of words. By learning these patterns， and by practicing them， you will master thousands of words.
Only the idle will be tired.
只有闲人才会感到疲倦。本段的主题句The purpose of this book is to provide you with practice in spelling English也是放在段落的开头，直截了当地告诉读者作者的写作意图，使读者对本段的主题思想有了明确的认识。
Give students a chance to grow. Do you mold them from one of a thousand patterns? Let them seek knowledge， but do not find it for them. Let them learn patience; do not force it on them. Let them take their own time to grow; do not set rigid time schedules. Most of all， do not push them against a stone wall， crushing them with knowledge gained from the experience of others. Experience cannot be taught; it must come slowly through personal search.
在这个段落中，主题句先不出现，而是先举出许多具体的experiences，在段落结尾时才予以归纳，得出中心结论：Experience cannot be taught; it must come slowly through personal search.这样的段落结构一开始容易使读者产生悬念，从而收到特殊的表达效果。
Most of us may have such experiences： when you go to some place far away from the city you live in and think you know nobody there， you are surprised to find that you should run into one of your old classmates in the street. Perhaps both of you would cry out，What a small world!
在这个段落里，作者先给出了一个假设性的事例，吸引读者的注意力，然后在段落结束时总结出What a small world!(世界真小啊)作为段落主题句。这样的段落有感染力，使读者有兴趣读下去。
Californians and New Englanders are both American. They speak the same language and abide by the same federal laws. But they are very different in their ways of life. Mobility—both physical and psychological—has made a great impression on the culture of Californians; lack of mobility is the mark of the customs and morality of New Englanders.