EX1:
10. b - be
11. d - to leave
12. a - would 
13. b - will sit
14. d - did not talk
15. a - what 
16. d - had
17. d - will go
18. c - redundant
19. c - walk
20. b - louder
EX2:
1. Unless you leave me alone, I will call the police.
2. If it didn't snow, we could go to school.
3. If you drink too much coffee, you can't sleep.
4. If you make me some coffee, I'll give you some sweets.
5. If he did not have to study for his exam, he could go out
6. If she weren't lazy, she could pass the exam.
7 . If he pays me tonight, i will have enough money to buy a car.
8. If he did not smoke too much, he could get rid of his cough.
9. If you study hard, you will pass the exam.
10. If you are impatient, you will make mistakes.
11. If i had eaten lunch, i would not feel hungry now.
12. If i have enough money, i will buy that book.