1. It began to rain, they had to stop their work.
2. Light travels in straight line is known to all.
3. Many people are worried about the possibility the computer will control the mankind.
4. My idea is we should do the work right away.
5. In his speech, the famous writer told us he had succeeded.
6. A writer is a person makes a living by writing.
7. There are 40 % people are in favor of the suggestion.
8. This is the place we first met.
9. She worked hard, failed the exam.
1。 they 前加so。后一句是一个表示结果的句子，并列连词so不能省。
2。 Light前加 That。that引导主语从句时，不能省略。
3. the computer前加that。that引导同位语从句时，不能省。
4. we 前加that。that引导表语从句时，不能省。
5。 he 前加how。从句意上可以看出，宾语从句缺少一个连接词how。
6. makes 前加 who。定语从句中关系代词作主语时,关系代词是不能省略的。
7. 第二个are 前加who。定语从句缺少主语。