參考答案：

　　1. The reason why Peter hasn’t come is that he didn’t catch the train.

　　2. He thinks it important that he does full preparation before the examinations every time.

　　3. Learning a foreign language well requires time and effort.

　　4. How to solve the problem will be discussed at tomorrow’s meeting.

　　5. It is polite for the student to give up his seat to the elderly woman.

　　6. It is no use debating with Tom, because he will never change his mind.

　　7. I’d rather lose the game than hurt him.

　　8. There seemed nothing else to do but send for a doctor.

　　9. It is said that the book has been translated into several foreign languages.

　　10. Ellen was absent this morning because she had her tooth filled.

　　11. I can’t have you running up and down all day long.

　　12. There was so much noise that the speaker couldn’t make himself heard.

　　13. It is not easy to be a host nation for the Olympics.

　　14. Adults are sometimes too busy to play.

　　15. The teachers don’t think it is difficult to learn English grammar.

　　16. It is very kind of him to give me so much help.

　　17. Those who pretend to know what they do not know will be punished one day.

　　18. To tell the truth, I didn’t know that they had already gone to Shanghai until yesterday.

　　19. Only by practice will you be able to improve your spoken English.

　　20. Nothing can give teachers more pleasure than to see the students’ progress.