首尾句作文是根据段首（尾）句续写短文。段首句作文也称主题句作文，因为作文题中所给的段首句往往是段落主题句。其特点是以题目为中心，一般情况下将文章分为三个段落，每段首句即为该段的主题句（topic sentences）。考生要按主题句的要求组织材料，提出论据，用一些辅助句（supporting sentences）来支持或说明主题句，写英文段首句作文要注意：所写的内容要紧扣主题，辅助句应围绕段首句续写。保证段内每个句子的内容与段首句紧密展开各个段落，如：例证、因果、定义、比较对比、程序等。要注意句与句之间，特别是段首句与辅助句之间的自然衔接。另外，所给的段首句有时是一个完整的句子，有时不是一个完整的句子，只是句子的一部分，这就要求考生一定要审好题。找出其中表示中心思想的关键词，围绕这些关键词去扩展、描述或说明。

　　［例1］Directions :For this part,you are allowed 30 minutes to write a composition about Women in the Modern World in three paragraphs. You are given the first sentence of each paragraph and are required to develop the idea in completing the paragraph; your part of the composition should be about 100 words, not including the words given. Remember to write clearly.

　　［范文］
　　Women in the Modern World
Women are playing an increasingly important role in society. Successful women who are government officials,writers, scientists,doctors and teachers can be found everywhere. It is true that many jobs that once were dominated by men can be done well by women.

　　With the changes in their social role,women?s position in the family has been improved as well.The husband is no longer the only bread maker in the family and the wife no longer lives on others.They share comforts and hardships with each other.

　　In spite of these changes, the liberation of women has not been completely realized. Women still face many difficulties and obstacles due to traditional roles and limited economic strength.Women still have a long way to go in their struggle for complete equality with men.

　　第一段首句是讲妇女在社会上的作用，因而续写的内容紧紧围绕妇女的社会作用，比如，妇女可以是政府机关的工作人员、科学家、教师等；第二句的段首句是关于妇女在家庭中的地位也提高了，续写的内容也是有关夫妻患难与共；第三句的段首句是讲妇女解放仍然任重而道远，续写的部分提出了妇女所面临的问题，整个续写的部分紧扣段首句。

　　［例２］Directions :Write a composition about What Would Happen If There Were No power in three paragraphs, you are given the first sentence or part of the first sentence of each paragraph:
1?Ever since early this century,electricity has become an essential part of our modern life.
2?If there were no electric power,...
3?Therefore,...

　　［范文］
　　What Would Happen If There Were No Power
　　Ever since early this century, electricity has become an essential part of our modern life. It has played a decisive role in the modern world. Everybody admits that development of our civilization depends on electricity.

　　If there were no electricity power, our modern world would be in trouble. For instance, all the wheel would stop because without the power the machine would cease working. And all the electrical equipment life would be impossible and in a great mass without electricity.

　　Therefore, we should make better use of elective power. On the other hand, we should educate people to economize on electricity and not to waste energy resources. At the same time we must do our best to exploit more electric resources to meet the requirements of human beings.

　　第一段的段首句是讲电已经成为人们现代生活中必不可少的部分，因而接下来的续写部分应强调它的重要性。第二段的段首句提出如果没有电的假设，下面列出没有电将会出现的麻烦。最后一段指出我们应该节约用电，开拓更多的电力资源。