1.
1. could
2. Can
3. can
4. couldn't
5. can't
6. couldn't
2.
1. She didn't have to study.
2. Jennifer had to pay the bill.
3. Does Susan have to go to the English course?
4. Jake needed to take a taxi.
5. Marcy dorsn't need to get up before six.
3.
1. could
2. should
3. Shall
4. don't have to
5. shouldn't
6. may
4.
1. ... could run for hours.
2. ... can't smoke ...
3. ... could relax.
4. ... can play outside ...
