在下列定语从句中填入适当的介词。
1. The pencil ____ which he wrote was broken.
2. He built a telescope ____ which he could study the skies.
3. The woman, ____ whom I learned the news, is a nurse.
4. The wolf____ which the sheep was killed was shot.
5. She has three children, all ____ whom are at school.
6. There is a tall tree outside, ____which stands our teacher.
7. My glasses, ____ which I was like a blind man, fell to the ground and broke.
8. In the dark street, there wasn't a person _____ whom she could turn for help.
9. I was surprised at the way ____ which he treated the old man.
10. The age ____ which children can go to school is seven.
11. His bike____ which he went to work was stolen last night.
12. Do you know the building ____ which is flying a red flag?
13. Ours is a beautiful school, ____ which we are proud.
14. The desk ____ which Jack is leaning is John's.
15. He bought a book yesterday, the author ____ which is a teacher.
