填入正确的引导词。

1. We are living in an age ____ many things are done on computer.

2. We are living in an age ____ we have a lot of things to learn about.

3. I can think of many cases ____ students obviously knew a lot of English

    words and expressions but couldn't write a good essay.

4. I can think of many cases ____ you know nothing about.

5. I want to know the date ____ you were born.

6. I have remembered the date ____ I forgot just now.

7. Do you know the reason ____ he is absent today?

8. That is the reason ____ I want to know.

9. This is the factory ____ his father works.

10. This is the factory ____ his father built.

11. The key ____ she was opening the door broke.

12. The library ____ we often go on Sundays is not far from our school.

13. No one knows the reason ____ she is leaving so early.

14. At last they came to a river ____ a new bridge is being built.

15. The old man always wears his glasses ____ he can't see anything.