after；     during；      pollute；     do；     pay for；      animal；     work

（1）China has made great progress　　the past forty years．

（2）We should be friendly to　　．We are all living in the same world．

（3）How much did you　　 your new bicycle？

（4）If the air is　　it is dangerous and will do harm to our health．

（5）My father is a good teacher who　　for his students day and night．