1. If you don't keep silent, you will wake the baby up.
2. If you don't stop talking, you won't understand the lesson.
3. If i knew her phone number, i would ring her up.
4. If i knew the answer, i could tell you.
5. If we had had a map, we wouldn't have got lost.
6. If Susan hadn't eaten four cream cakes, she wouldn't have felt sick.
7. If he hadn't been late every day, we wouldn't have lost his job.
8. If he Peter didn't eat so many chips, we wouldn't be fat.
9. If Robert hadn't started smoking cigarettes, he wouldn't have got a bad cough.
10. If he didn't have to study for his exam, he could go out.
11. If you aren't good, your parents will be very unhappy.
12. If you don't do it carefully, you'll feel sorry afterwards.