题目内容：

根据句意用所给单词的适当形式填空。

1. It is ______________(nature) for a bird to fly.

2. It is ____________(polite) to ask a woman her age in western countries?

3.Our English teacher likes reading ____________(educate) books.

4. I like ____________(lie) on the grass in the sun in spring.

5. Do you think noise _____________(pollute) is a terrible problem?