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1. I don't think those boys should play football on the street because it is very dangerous.
2. I don't think she shouldn't stay in bed all day unless she is ill.
3. I think this medicine should be kept in cool place.
4. I think you should drive carefully because of the heavy rain.
5. Had she driven carefully, she wouldn't have been in the accident.
6. Had you listened to my advice, you wouldn't have been in the mess.
7. Had I known your problem, I would have given you a hand.
8. Had we left later, we would have missed the train.

II/
1. If my car hadn't broken down when I was leaving, I could have come on time.
2. If Linda hadn't been exhausted, she would have got some sleep last night.
3. If I had enough time, I could take much exercise.
4. If there were some truth in her words, I would believe in her.