II/

9. contaminated 

III/

16. I am a member of the anti-pollution program in my school. I often go to school by bus (so)

=> I am a member of the anti-pollution program in my school so I often go to school by bus. 

17. The street in this area were cleaned off. Public facilities would be constructed.(because of)

=> Public facilities would be constructed because of having cleaned off the streets in this area. 

18. Fresh, clean water is very important to life. No one can live long without it (since)

=> Fresh, clean water is very important to life since no one can live long without it. 

19. Kim never cleans her room. Her mother is complaining (because)

=> Kim’s mother is complaining because Kim never cleans her room. 

20. Many aquatic animals are dead. The water is polluted (due to)

=> Many aquatic animals are dead due to water pollution.

@nguyễn