2.
Join each pair of sentences into a single sentence, using if:
- You refuse to pay the money. Then you will be imprisoned.
 - Perhaps he will agree. I shall be delighted then.
 - I would write to Michael now. But I don't know his address.
 - They will pay you more next month. But you must work harder.
 - You must be careful. Otherwise, you will have an accident.
 - The leader of the gang may find the house empty. In that case, he will whistle to the rest of the gang to join him.
 - You could have fixed everything properly yesterday. I would not have had any worries.
 - He looked around. Otherwise, he would have been hit by the bus.
 - You can see the island from here. But the day must be very clear and bright.
 - The pilot didn't know about storm over the mountains. He certainly wouldn't have taken off in that direction.