Exercise 1.

1.her

2. Bob's

3. My

4. Students'

5. your

6. our

7. his

8. girl's

Exercise 2.

1. has

2. are

3. has

4. were

5. am

6. have

7. had

8. is

9. were

Exercise 3.

1. some

2. any

3. some

4. any

5. no

6. some

7. some

8. no

Exercise 5.

1. could

2. couldn't

3. had to send

4. had to sign

5. might change

6. might not