1. 根据句意及汉语提示完成单词。

1. （1） It's our duty to protect our (环境) well.

3. （2） No one knows exactly how large the (宇宙) is.

5. （3） You should (交流) with your parents more often.

7. （4） How many (组) are there in your class?

9. （5） The (系统) can translate English into Chinese.