第一讲 段落简介
1.1段落
段落是构成文章的一组句子。段落必须表达完整的意思：或描写事物，或争论某事，或对某事提出疑问，或要求什么，或给事物下定义，或驳斥某观点。
1.2典型段落的构成
一个典型的段落通常由三部分组成：（1）主题句；（2）说明或支持主题的推展句；（3）结论句（有些段落没有该部分）。
示范段落1-1
We all know that cigarette smoking is a dangerous habit because it causes health problems. Doctors say it can be a direct cause of cancer of the lungs and throat and can also contribute to cancer of other organs. In addition， it can bring about other health problems such as heart and lung diseases. It is clearly identified as one of the chief causes of death in our society.
1.3示范段落分析
这是一个典型的段落，可概括提纲如下：
主题句： We all know that cigarette smoking is a dangerous habit，because it causes health problems.
推展句： 1. Doctors say it can be a direct cause of cancer of the lungs and throat and can also contribute to cancer of other organs.
2. It can bring about other health problems such as heart and lung diseases.
结论句： It is clearly identified as one of the chief causes of death in our society.
从以上提纲可见，主题句提出了一个问题： What kind of health problems does cigarette smoking cause？随后的两个推展句回答了这个问题，结论句总结了推展句并再一次强调主题句。
Exercise 1-1
Directions： Read the following paragraphs and find out the topic sentence， the supporting details and the concluding sentence， if there is one.
（1）
The need for wildlife protection is greater now than ever before.About a thousand species of animals are in danger of extinction，，and the rate at which they are being destroyed has increased. With mammals， for instance， the rate of extinction is now about one species every year； from A. D. 1 to 1800， the ratewas about one species every fifty years. Everywhere， men are trying o solve the problem of preserving wildlife while caring at the same time for the world‘s growing population.
Topic Sentence：____________________________________________
__________________________________________________________
Details： 1.________________________________________________
__________________________________________________________
2._______________________________________________________
__________________________________________________________
Concluding Sentence：________________________________________
__________________________________________________________
（2）
The Americans and the British not only speak the same language but also share a large number of social customs.For example， in both America and England， people shake hands when they meet each other for the first time. Also， most English men will open a door for a woman or offer their seat to a woman， and so will most Americans. Promptness is important both in England and in America. That is， if a dinner invitation is for 7 o‘clock， the dinner guest either arrives close to that time or calls up to explain his delay.
Topic Sentence：____________________________________________
__________________________________________________________
Details： 1.______________________________________________
__________________________________________________________
2._______________________________________________________
__________________________________________________________
3.________________________________________________________
__________________________________________________________
Concluding Sentence：________________________________________
__________________________________________________________
（3）
Birds use many different materials to build nests.Some birds use bits of grass. The tailor-bird of Africa and India uses grass to sew leaves together. Other birds find twigs and pebbles useful.
Topic Sentence：_____________________________________________
__________________________________________________________
Details： 1._____________________________________________
__________________________________________________________
2.______________________________________________________
__________________________________________________________
3.______________________________________________________
__________________________________________________________
Concluding Sentence：_______________________________________