用合适的介词或副词填空。
1. I called him yesterday, but he was ______ work.
2. I often take my dog ______ to the park ______ a walk.
3. I have many books ______ animals. These books help me learn a lot ______ how to keep animals.
4. That mountain looks ______ an elephant's trunk.
5. I'm afraid ______ big dogs.
6. The new computer doesn't belong ______ me. It's my father's.
7. He is interested ______ nothing.
8. The next morning the ground was covered ______ snow.