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1. If you don't keep silent, you'll wake the baby up.
2. If you don't stop talking, you won't understand the lesson.
3. If we had had time, we would have visited the museum.
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 my brother knew English, my brother could apply for that job.
7. If you don't study harder, you'll fail in the next exam.
8. If he hadn't been late every day, he wouldn't have lost his job.
9. If Susan didn't eat too much chocolate, she wouldn't be overweight. 
10. If Robert hadn't started smoking cigarettes, he wouldn't have got a bad cough.
11. If you don't hurry up, you will be late.

12. If she weren't very busy, she could help me now.
13. If you took exercise, you wouldn't be unfit.
14. If you are not careful, you will cut yourself with that knife.
15. If he had studied his lessons very carefully, he wouldn't get bad marks now.
16. If Dick didn't drive carelessly, he wouldn't often cause accidents.
17. If Jame hadn't helped me, I wouldn't have been able to move the table.
18. If I had known that you were in hospital, I would have visited you.