根据句意用所给单词的适当形式填空。

1. Noise _____ (pollute) isn't a big problem of our city.

2. It is _____ (please) to go hiking with old friends.

3. She danced _____ (beautiful) at the party yesterday.

4. Don't be afraid of the dog. It is _____ (harm).

5. It's _____ (mean) to help the poor people.

6. —Why won't you see the movie this afternoon?  

    —Because I _____ (see) it before.

7. When I arrived there, Millie_____ (read) a book.

8. I wish we _____ (will) have enough  money to help the poor.

9. It's impossible for him _____ (do) the job alone.

10. Although it's very late, the workers  keep _____ (work) hard.

液压缸是液压系统中的（）元件。

A、动力

B、控制

C、执行

D、辅助