I.
12. C. of
13. B. me to do
14. B. theirs
15. C. roof
16. C. mustn't
17. A. autumn
18. A. a very intelligent student
19. B. take
20. B. playing
II.
1. will see / are going to see
2. don't usually go
3. protect
4. is raining
5. to buy
III.
1. biggest
2. pollution
3. length
4. nationality
5. mountainous
6. friendly
7. neighborhood
8. businessman
9. shopping
10. rainy