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2. Researches on global warming were begun to carry out by scientists two years ago.
3. Julie is practicing the piano so as to play for the party.
4. If the airport hadn't been closed, she would have flown to Rome.

2/
1. If we had had enough money, we would have gone on holiday.
2. Exercises won't be corrected by the teacher tomorrow.
3. It was not until the age of 24 that she stopped learning German.
4. He moved to the front row in order to hear the speaker better.

3/
1. It was not until Lan was 35 that she went abroad.
2. A great deal of tea is drunk in England.
3. We hurried to school yesterday not to be late.
4. If he had had the ticket to the game, he would have been able to get in.