主题句的写作要求
1.完整的结构
Fragment: Teaching a child good manners.
Complete: Teaching a child good manners is fun. / Teaching a child good manners is no easy task. (分别以这两句为主题句的段落，其发展方向肯定会不同。) Fragment: The importance of blood.
Complete: Blood serves our body in three important ways.
2.明确的观点
Unclear: I know Smith.
Clear: Smith has a good sense of humor.
Smith is the meanest man I ever know.
Unclear: People care about sports. /Sports influence our life.
Clear: Sports can keep people healthy and strong.
Sports benefit us in many ways.
Sports have their negative aspects.
Sports sometimes can do some harm to people.
3.具体的内容
General: Electricity is important.
Specific: Electricity has become an essential part of modern life. /If there were no electric power, our modern world would be in trouble.
练习：
I 选出与下列主题句不符的扩展句：
1.. The sense of humor is mysteriously bound up with national
characteristics. A Frenchman, for instance, might find it hard to laugh at a Russian joke. In the same way, a Russian might fail to see anything amusing in a joke which would make an Englishman laugh to tears.
A. There are always different jokes.
B. My brother often makes jokes.
C. Jokes, despite their differences, have the same humor.
D. Whether we find a joke funny or not depends on where we have been brought up.
2.. Retirement gives one a feeling of uselessness. Such a
psychological problem often brings physical problems. It is the feeling of emptiness that gradually kills the retired. With retirement there will be a decrease in income. Unless they plan carefully, the retired will get into economic problems.
A. The retired are a problem of our society.
B. People should not retire until unable to work.
C. Retirement can bring many problems for the retired.
D. We should do something for the retired.
3.. They now can do most of the things people can do, though
most scientists agree that computers cannot take the place of humans. Who knows what the computers of tomorrow will be like? Will they make life better, or will they bring suffering to people? People today will have to decide how to use the computers of tomorrow.
A. Computers are a great helper.
B. Computers compete with man for jobs.
C. Recently there have been great changes in computers.
D. We need greater efforts to develop computers.
4.. For example, there are so many idioms in English. Another
example is the spelling. Learners have to spend a lot of time learning them by heart. And they must put practice into the first place. The more they practice, the more they would benefit. So English learners are required to speak more and read more. English becomes easy only in practice.
A. You have to make greater efforts to learn English well.
B. To learn English well, you should practice more.
C. English, as a language, has its difficult points to learn.
D. English is a special language.
5.The human brain is at least 10.000 times more complex than a computer. What’s more,
computers cannot make decisions on their own. They need detailed instructions from human beings in order to operate. .
A. So computers are great inventions.
B. So a computer is a computer.
C. So they need further development.
D. So computers can never replace human brains altogether.
(说明：本例中主题句在段尾，与段尾句重合。如果将主题句至于段首，则可以写成：Despite all their advantages, computers can never replace the human brain.)
II 改写下列句子，使其成为合适的主题句：
1.Poor: I am going to talk about advertisements.
Improved:
2.Poor: We are dependent upon the sun.
Improved:
3.Poor: Water is necessary.
Improved:
4.Poor: I like sports.
Improved:
5.Poor: Learning a foreign language is difficult.
Improved:
III 给下列段落加上主题句：
1.. One factor is the amount of sunlight received. Altitude,
or the height above sea level, also determines climate. The oceans have an effect on the climate of adjacent land. In addition, climate is influenced by general circulation of the
