11. We wouldn't have had a problem if you (haven't/ hadn't) mentioned it to Tony.

12. If you (would/ should) happen to bump into James, ask him to call me, would you?

13. We should take our tent with us (in case/ unless) we can't find rooms to stay in.

14. If you had been more careful, you wouldn't (have/ have had) an accident.

15. If he (was / had been) born two hundred years later, would Mozart have become a pop star?

16. (Unless/ Otherwise) we pay the electricity bill soon, they might cut us off.

17. It would have been a boring film (but for / if not) the action scenes, which were excellent.

18. We'll hire a car when we get there, (supposing/ providing) it's not too expensive.