Объяснение:

3. 1. If we have enough money, we will travel abroad.

2. If the oil prices falls,our economy won't get profit.

4.1. If all the spare hadn't been available by yesterday, we wouldn't have delivered them to our buyers.

2. If Tom had lent the money, I would have bought a new car.

3. If I had worked hard during the term, I wouldn't have failed all the exams.