IV. Modal Verbs in the Past. Rewrite each sentence so that it contains can’t, might, must, should or needn’t.
1. I’m sure that David took your books by mistake.
2. It was a mistake to park outside the police station.
3. I’m sure that Liz hasn’t met Harry before.
4. It was unnecessary for you to clean the floor.
5. Heather possibly hasn’t left yet.
6. I’m sure they haven’t eaten all the food. It’s not possible!
7. Jack is supposed to have arrived half an hour ago.
8. Perhaps Pam and Tom decided not to come.
9. I think it was the cat that took the fish from the table!
10. It was a waste of time worrying, after all!

1. David must have taken your books by mistake. 2. They shouldn't have parked outside the police station. 3. Liz can’t have met Harry before. 4. You needn't have cleaned the floor. 5. Heather might not have left yet. 6. They can’t have eaten all the food. It’s not possible! 7. Jack should have arrived half an hour ago. 8. Perhaps Pam and Tom might have decided not to come. 9. It must have been the cat that took the fish from the table! 10. It must have been a waste of time worrying, after all!