Modal verbs revision

Fill in the gaps with the appropriate modal verb. 1. You've got plenty of time. You don't need to not have to hurry.2. There's a knock at the door. I'm expecting Paul. It must be him.3. Can / could ask you a question?4. I don't have togo to work on Saturdays. It's my day off.5. She can't be 35. She looks older than that.6. Tom has given me a letter to post. I mustn't / shouldn't forget to post it.7. Ann stayed in bed this morning because she didn't have to go to work.8. He couldn'tplay chess when he was young.9. You can drive a car when you're 18.10. Jack spends the whole day walking around. He can't have a job.11. My mother keeps telling me that we must / have to wash our hands before we sit down at the dinner table.12. When I was a child I couldn't understand adults, now that I'm an adult I can't understand children.13. Sally looks sad and worried. She must have a problem with something.14. Could I see your passport, please.15. I had to take a taxi because the bus didn't come.16. She shouldn't speak so rudely to her parents.17. The teacher always tells us we must not cheat during a test.18. I couldn't stop laughing. The joke was so funny.19. Can / could you turn down the volume? It's too loud.