Choose the best alternatives.1) I can039;t / don039;t have to go

Choose the best alternatives.
1) I can't / don't have to go out. Im too busy.
2)We don't have to / can't catch a taxi. ill drive.
3)I have to \ can go into the army for a year. I don't have a choice.
4)You shouldn't \ don't have to smoke during meals - it's annoying.
5)I should/ have to do more exercise. Im putting on weight.
6)You can / should see the doctor at 5pm on Thursday. That's the earliest time she is free.