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.