b
2 Doctors don't have to be good at painting.
3 A teacher doesn't have to know everything.
4 We have to do the washing-up after lunch.
5 You don't have to get up early tomorrow.
6 Roberto doesn't have to work during the holidays.
c
2 havу to
3 has to
4 have to
5 doesn't have to
6 don't have to