Câu trả lời:
1. If it doesn't stop raining, we won't go out.
2. You didn't cook as well as her.
3. We can only get into the house if someone has a key.
4. If we had had enough money, we would have gone on holiday.
5. My father allowed me to use his car.
6. Researchers on AIDS began to be carried out by scientists in 1980.