I.
1. C
2. B
3. C
4. D
5. A
6. A
7. C
8. A
9. B
10.A
II.
11. D
12. D
13. A
III.
14. D
19. A
20. C
IV.
17. If you hadn't stayed up very late last night, you wouldn't be tired now.
18. I wish I hadn't eaten too much ice-cream.
19. Had I not been busy, I would have watched TV last night.
20. If only my father were here now.