3. 因果关系

　　在段落一开头，就用主题句点明其因果关系，然后选用有关材料，客观的罗列某些原因或结果，以阐述中心思想。

　　Growing numbers of well-to-do Americans are making the decision to move abroad. They find it impossible in America to walk the streets at night without fear of being raped, mugged, or murdered, nor do they see a way to escape the poisonous air of the cities. They maintain that even American food has become increasingly dangerous to eat. Last but not least, they insist that they are sick of the pace of American life, a pace that leaves no time for relaxation or pleasure。

　　因果关系常用语汇：

　　because of, so, owing to, thanks to, thus, as a result of, hence, for this reason, consequently, is caused by, lead to, result in

　　4.比较法

　　主题句必须明确表明所要比较的对象和所要比较的范围，实际上就是罗列两个或两个以上比较对象的相同点。

　　Learning English is like building a house. Laying a solid foundation is the first and most important step. In other words, you should read and speak English every day. Memorizing new words and phrases is also helpful. Like building a house, learning English takes some time。

　　So don’t be impatient. Remember, Rome wasn’t built in a day。

　　常用语汇：at the same time, similar to, accordingly, both, show a degree of similarity, similarly, the same as, and„ too, in the same way, in a like manner

　　5.举例法

　　列举事实或举出实例来说明中心思想， 是简单易行、具有说服力的写作方法。

　　Communicating with other people by telephone is very convenient,

　　especially when you have something urgent. For example, if one of your family members is seriously

　　ill at night, and you don’t know how to deal with it and where to find a doctor, what can you do? A telephone is the answer. Dial 120 and you will get services from the hospital very soon。