1. 用所给单词的适当形式完成句子

1. （1） We need to drink (much) water on hot days.

3. （2） When there is enough water in the clouds, it (fall) as rain.

5. （3） Look! The boy (waste) water. We should stop him.
   

7. （4） Jack (drop) a small stone into the water.
   

9. （5） Some foods are unhealthy because there are (chemical) in them.

11. （6） If you are tired, please stop _(work) to have a rest.

13. （7） Lucy, do you know how the clouds (form)?

15. （8） To stay healthy, it's best not to(add) too much cooking oil to dishes.

17. （9） Dad, I can't stand the food you cooked. It is too (salt).

19. （10） The water in this river isn't (drink) because it is polluted