2. Yes, I know that I __________ studied last night, but I decided to watch TV instead.
would've
should've
must've

3. Where's Jill? She __________ forgotten that we were supposed to meet at 2:00 PM.
would've
should've
must've

4. I __________ been glad to help you. Why didn't you ask?
would've
could've
must've

5. Look! It's raining and Professor Johnson is all wet. He __________ forgotten his umbrella again!
should've
would've
must've

6. You __________ turned off the computer when you did! You've caused all kinds of problems!
shouldn't have
must not have
might not have

7. She __________ study last night, so she didn't.
didn't have to
mustn't
didn't ought to

8. Yes, she __________ been here yesterday. I don't think she was, but I can't prove that she wasn't.
could
could've
couldn't have

9. I'm not sure where Dave is. He __________ taken Benjamin to a movie or to the zoo.
would have
may have
ought not to have

10. You shouldn't have driven so fast! You __________ had an accident!
would have
may have
might have