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.