1
2.can't
3 couldn't
4 could
5 couldn't
6.can't
7. could
8.could
2.
A doctor must work long hours.
A doctor must wash his/her hands regularly.
A doctor mustn't be rude to patients.
A doctor must rest well each night.
A doctor mustn't work when she/he is ill.
A doctor must care about his/her patients.