torical
sentence）
example： how do you think people will solve the problem of wildlife
protection？
3）不完整句（fragments）
example： and the workingman？
初学者最好使用肯定句作为主题句。
2.3主题句的位置
主题句出现的位置有以下四种情况：
1）段首（at the
beginning）
主题句经常居于段首，以便读者浏览主题句就可掌握文章的概要。这个位置适用于写提供信息或解释观点的段落。
2）段末（at the end）
用推理方法展开段落时，主题句往往位于句末。
3）段中（in the
middle）
有时为了使段落多样化，主题句也可以居于段中。
4）隐含（implied）
有时候，尤其在写叙述性或描写性段落时，当所有的细节都围绕着一个显而易见的主题时可以不用主题句。
exercise 2-1
directions： read the following paragraphs and identify the topic sentence. if it is implied， summarize it yourself.
（1）
but no matter what it is called， all polyester has certain good points. it does not wrinkle easily. it dries quickly after it is washed. it holds its shape. it is strong and keeps its colors well.
topic sentence：____________________________________________
position：________________
（2）
black is the colour of mourning. red symbolizes danger，violence，or bloodshed. if you are afraid， you are yellow. none of these sayings is true outside the english speaking world. in china and korea， white is the color of mourning. in russia red stands for beauty
and life. in italy and
germany you are yellow with anger，not with fear.
topic sentence：_____________________________________________
position：__________________
（3）
our chief source of fresh water is rainfall that collects in lakes，rivers， and reservoirs. recently， however， we have discovered anew source， aquifers， which are rock formations
containing water.even under
deserts， vast
aquifers may be waiting to be tapped.companies drilling for oil in the middle east have sometimes struck
aquifers， which
provide unexpected water supplies for arid regions.
topic sentence：____________________________________________
position：_____________
（4）
suppose you’re playing a game. you make a silly mistake and lose. do you become angry？ or can you laugh at yourself and hope to do better next time？ suppose you are at a special
dinner.you
accidentally spill some food.why keep worrying about how clumsy you look？why not laugh it off and enjoy yourself
anyway？if you can， it’s good sign you've really grown up.
topic sentence：____________________________________________
position：____________
（5）
young men sometimes bring edelweiss back for their girlfriends. the girls think of the flowers as
a proof of true love.mountain climbers， guides， and hunters pick edelweiss too.they wear it on their hats. to them it is a sign of courage and daring.
topic sentence：____________________________________________
position：____________
第三单元 如何写好主题句
3.1关于写主题句的建议
1）要写合乎语法的句子
example 1： two causes of the american civil war.
这个句子是个不完整的句子，不合乎语法，因此不能用作主题句。
example 2： there were two causes that led to the american civil war.
重写后的句子合乎语法，是个较好的主题句。
2）要使用限写词限定主题
为了正确表达观点，好的主题句经常使用关键词或词组，即限制词（controllers）限制这一观点。
example 3： air travel is more convenient than train for at least three reasons.
从上例主题句我们得知作者将要写“air travel”（ topic），他将要把 “train”（ aspect）和“ air travel”作比较，并且陈述“reasons”。由此可见，作者在“aspect”（方面）和“reason”（原因）两方面限制他的主题。
3）要注意主题的可写性
所定的主题不能太笼统，也不能太具体。
example 4： in hemingway's story “soldier’s home”，krebs tells
his mother that he wants no part of god's kingdom.
这个句子太具体以至于无东西可写，无法展开段落。
example 5： in hemingway's story “soldier’s home”， kreb is a
lonely， cynical
veteran.
这个句子可作为主题句，因为可以围绕“lonely，cynical”展开段落。
example 6： let me tell you something about overpopulation.
这个句子太笼统，作为一个段落的主题太大，难于驾驭。
example 7： why has the world population been increasing sorapidly in the last
decades？
这个句子是个较好的主题句，作者用“the reasons for
overpopulation in the last decades”，从“原因”（cause）和“时间”（time）两方面限制了主题，能在一个段落内论述。
exercise 3-1
directions： identify the areas which limit the topic sentences.
3.1.1 soccer has become increasingly
popular in the u. s. in the last ten years.
topic：_____________
limitations：________________________________________________
3.1.2 pollution has caused three major
problems in the last decades.
topic：______________
limitations：________________________________________________
3.1.3there are two kinds of memory： short-term and long-term.
topic：____________
limitations：________________________________________________
3.1.4 women are playing an increasingly
important part in society today.
topic：____________
limitations：________________________________________________
3.1.5 women are paid less for equal
work than men in some companies.
topic：____________
limitations：________________________________________________
exercise 3-2
directions： write two topic sentences for each of the topics，limiting the topic in different
ways.
3. 2. 1 topic： the study of english
topic sentence 1：__________________________________________
topic sentence 2：__________________________