12. Peter could get good marks if he studied hard.
13. If my sister didn't have terrible headache, he wouldn't be absent from her class.
14. If Windy had come, we wouldn't have cancelled the meeting.
15. Unless he had been angry, he would have said something.
16. If you don't help me, I'll fail again.
17. If my house weren't guarded by two big dogs, it would be broken into every night.
18. If we don't go, we will be late.
19. If you are impatient, you will make mistakes.
20. If I were you, I wouldn't buy it.
21. If he polished his shoes, he would look smart.
22. If I were tall enough, I would join the basketball team.
23. Unless you leave me alone, I'll call the police.
III/
1. If Rita had got some sleep last night, she wouldn't be exhausted today.
2. If he saw the signal, he would stop his car.
3. If Peter had prepared his lessons well, he wouldn't get bad marks