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4. If David weren't clumsy, he wouldn't have many accidents.
5. If I weren't busy, I would write to my friends regularly.
6. If Sandra arrives a bit early, she can help you get things ready.
7. If the bus weren't always so crowded, I would ride the bus to school every morning.
8. If the office is closed, Mike will be able to get in.
9. If people realised how important it was to conserve energy, they would do something about it.
10. If you want a chat, just give me a ring.
11. If it doesn't stop raining, we won't finish the game.
12. If the driver in front hadn't stopped suddenly, the accident wouldn't have happened.
13. If the airport had not been closed, Sarah would have been able to fly to Rome.
14. If Carol hadn't been studying, she would have answered the phone.
15. If I had had an umbrella, I wouldn't have got wet in the rain.