请找出下列各句中的错误并加以改正。

　　1. This is the factory where we visited last week.

　　2. This is the watch for which Tom is looking.

　　3. The person to who you spoke is a student of Grade Two.

　　4. The house in that we live is very small.

　　5. The sun gives off light and warmth，that makes it possible for plants to grow.

　　6. I’ve read all the books which I borrowed from the library.

　　7. This is the best film which I have ever seen.

　　8. My father and Mr. Smith talked about things and persons who they remembered in the country.

　　9. Everything which we saw was of great interest.

　　10. His dog，that was now very old，became ill and died.

　　11. The reason which he didn’t go to school is that he was ill.

　　12. Those who wants to go with me put up your hands.

　　13. The boy，his mother died last year，studies very hard.

　　14. I have two sisters，both of them are doctors.

　　15. We’re going to visit the school where your brother works there.

　　16. He is the only one of the students who have been invited to the English Evening.

　　17. That is the way which they work.

　　18. Those have questions can ask the teachers for advice.

　　19. Who is the man who has white hairs？

　　20. I will never forget the days which we had a good　time together at the sea.[1][2]