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.