2主题句在文中；
3主题句在文末；
4主题句以首尾呼应的形式出现在文首和文末。
1. 主题句在文首 这类文章写法上的特点是文章的第一句起着点题的作用，概括了文章的主要内容或信息，下文接着对主题句所涉及的话题进行具体的阐述。如全国高考题 A JINTAN, JIANGSU The 20 students 18 boys and 2 girls had a thousand reasons to be proud of themselves. They had just climbed their way to the top rung阶梯out of 4 million students taking part in the Fifth National Hua Luogeng Gold Cup Mathematics Contest 竞赛on Tuesday evening. The 20 gold medal winners are all primary and middle school students under the age of 14. “Many of the problems are of college level and these pupils can figure them out. It is just unbelievable“ said a teacher from Guangdong province. Named after Chinas most famous mathematician, Hua Luogeng, the contest started in 1986, one year after his death. In less than 10 years, it has been recognized by the State Education Commission国家教委 as the countrys biggest and best contest of its kind. This news story is mainly about ______. A. when the contest started B. how the contest got its name C. the 20 pupils who have won gold medals in the contest D. the 5th National Hua Luogeng Gold Cup Mathematics Contest 【分析】这是一篇报道，文章的第一段只有两句话“20个学生2女18男有充分的理由为自己感到自豪，因为他们夺得了第五届华罗庚杯数学竞赛的金奖，是4百万参赛学生中的佼佼者”，下文接着对竞赛的有关情况进行报道，因此，第一段实际上就是这篇报道的主题句。A、B、C分别只包含了报道的部分信息，显然不合题意；
D选项与主题句的意思完全一致，因此是正确答案。
2. 主题句在文中 这类文章写法上的特点是开始部分是引题，接着是点题，最后是对主题进行叙述，主题句常常起着承上启下的作用。如全国高考题 Fat on human beings is distributed in different ways. Some fat people have a large stomach and no waistlinewhich makes them look round, rather like apples. Others are fatter below the waist, which makes them appear pear-shaped. There are two types of fat external fat fat under the skin and internal fat fat inside the body wall. Doctors, who have been examining the relationship between health and fatness, have found that the pears have less internal fat, but the apples have more internal fat than external fat. This seems to be what causes the health problems. The best treatment for fatness is to reduce the internal fat. But unfortunately it seems that dieting 节食 simply makes an apple-shaped person into a smaller apple and a pear-shaped person into a smaller pear. At the moment there is no known way of reducing the internal rather than external fat. The text is mainly about ______. A. fatness and health B. ways to lose weigh C. peoples figures D. distribution of fat 【分析】该文的第一段交代了脂肪在体内的分布状况；
第二段交代了脂肪的种类及不同种类的脂肪与健康之间的关系；
第三段讲的是减肥应该减掉哪一类脂肪以及节食存在的问题。很明显，第二段，特别是第二段的第二句，起着承上启下的作用，是该文的主题句。A选项符合主题句的意思，应该是正确答案；
B选项与文章的意思无关；
可以排除；
C、D选项分别只与文章的部分信息有关，也可以排除。
3. 主题句在文末 这种写法的特点是在叙述完某件事情或某个话题之后，用一句话交代事情的结果或对前面的叙述进行归纳。如广东高考题 In 1901, H.G. Wells, an English writer, wrote a book describing a trip to the moon. When the explorers 探险者 landed on the moon, they discovered that the moon was full of underground cities. They expressed their surprise to the “moon people“ they met. In turn, the “moon people“expressed their surprise. “Why,“ they asked, “are you traveling to outer space when you dont even use your inner space“ H.G. Wells could only imagine travel to the moon. In 1969, human beings really did land on the moon. People today know that there are no underground cities on the moon. How ever, the question that the “moon people“ asked is still an interesting one. A growing number of scientists are seriously thinking about it. Underground systems are already in