1. Don't talk about such things of _______ you are not sure. 

2. Is this the factory __________ you visited the other day? 

3. Is this factory __________ some foreign friends visited last Friday? 

4. Is this the factory __________ he worked ten years ago? 

5. The wolves hid themselves in the places __________ couldn't be found. 

6. The freezing point is the temperature __________ water changes into ice. 

7. This book will show you __________ can be used in other contexts.. 

8. The reason is __________ he is unable to operate the machine. 

9. I'll tell you __________ he told me last week. 

10. That tree, __________ branches are almost bare, is very old. 

11. I have bought the same dress __________ she is wearing. 

12. He failed in the examination, __________ made his father very angry. 

13. We're talking about the piano and the pianist _______ were in the concert we attended last night. 

14. The girl ________ an English song in the next room is Tom's sister. 

15. Those _______ not only from books but also through practice will succeed. 

16. Anyone ________ this opinion may speak out. 

18. Can you lend me the novel ______ the other day? 

20. ---- "How do you like the book?"
     ---- "It's quite different from _______ I read last month." 

21. Mr. Zhang gave the textbook to all the pupils except _______ who had already taken them. 

22. The train _______ she was travelling was late. 

23. He has lost the key to the drawer _______ the papers are kept. 

24. Antarctic _______ we know very little is covered with thick ice all the year round. 

25. It's the third time _______ late this month. 

26. It was in 1969 _______ the American astronaut succeeded in landing on the moon. 

27. May the fourth is the day ______ we Chinese people will never forget. 

28. We are going to spend the Spring Festival in Guangzhou, _______ live my grandparents and some relatives. 

30. Is it in that factory _______ "Red Flag" cars are produced?