Unit 20

                 Exercise 10
1. c
2. e
3. d
4. b
5. a
               Exercise 11
1. must
2. might
3. can't
4. may
5. could
            Exercise 14
1. She must come back
2. He might have lost his way
3. She could have forgotten the appointment
4. She can't have been commited the crime
5. He must have stolen the money
6. He might have lied to you
7. They may have been sleeping when you called them
8. She might be working in her office
9. He mustn't paid the rent