1. 根据句意及首字母提示完成单词。

1. （1） Drinking is a principal c of traffic accidents.

3. （2） She had spent all her life working in the (工厂).

5. （3） I feel it is our duty not to p our environment.

7. （4） Cats and mice have always been natural .(敌人)

9. （5） My father works in the (石油) industry.