1. It may cost $100.

a) It may not cost $100.
b) May it cost $100?

2. Men should help with the housework.

a) Men shouldn't help with the housework.
b) Should men help with the housework?

3. Tom would pay her.

a) Tom wouldn't pay her.
b) Would Tom pay her?

4. They could play the guitar.

a) They couldn't play the guitar.
b) Could they play the guitar?

5. We're seeing Mary tomorrow.

a) We aren't seeing Mary tomorrow.
b) Are we seeing Mary tomorrow?

6. She ought to keep it in the fridge.

a) She ought not to keep it in the fridge.
b) Ought she to keep it in the fridge?

7. You can understand it.

a) You can't understand it.
b) Can you understand it?

8. The police were watching the house.

a) The police weren't watching the house.
b) Were the police watching the house?

9. You can go with him.

a) You can't go with him.
b) Can you go with him?

10. They've got a house.

a) They haven't got a house.
b) Have they got a house?

11. Your boss will be angry.

a) Your boss won't be angry.
b) Will your boss be angry?

12. Tom should pay the fine.

a) Tom shouldn't pay the fine.
b) Should Tom pay the fine?

13. They may come tonight.

a) They may not come tonight.
b) May they come tonight?

14. They were cleaning their shoes.

a) They weren't cleaning their shoes.
b) Were they cleaning their shoes?

15. He must write in French.

a) He needn't write in French.
b) Must he write in French?

16. You have read the instructions.

a) You haven't read the instructions.
b) Have you read the instructions?

17. These pearls are made by oysters.

a) These pearls aren't made by oysters.
b) Are these pearls made by oysters?

18. The ice was thick enough to walk on.

a) The ice wasn't thick enough to walk on.
b) Was the ice thick enough to walk on?

19. This will take a long time.

a) This won't take a long time.
b) Will this take a long time?

20. They may (permission) take the car.

a) They may not take the car.
b) May they take the car?

21. You've made a mistake.

a) You haven't made a mistake.
b) Have you made a mistake?

22. Ann would like a skiing holiday.

a) Ann wouldn't like a skiing holiday.
b) Would Ann like a skiing holiday?

23. We must do it at once.

a) We needn't do it at once.
b) Must we do it at once?

24. Tom could come.

a) Tom couldn't come.
b) Could Tom come?

25. They were in a hurry.

a) They weren't in a hurry.
b) Were they in a hurry?

26. There is enough salt in it.

a) There isn't enough salt in it.
b) Is there enough salt in it?

27. You could see the sea from the house.

a) You couldn't see the sea from the house.
b) Could you see the sea from the house?

28. Ann will be able to drive you.

a) Ann won't be able to drive you.
b) Will Ann be able to drive you?

29. They had written to him.

a) They hadn't written to him.
b) Had they written to him?

30. We must cook it in butter.

a) We needn't cook it in butter.
b) Must we cook it in butter?

31. It is freezing.

a) It isn't freezing.
b) Is it freezing?

32. She ought to accept the offer.

a) She ought not to accept the offer.
b) Ought she to accept the offer?

33. There'll be time for tea.

a) There won't be time for tea.
b) Will there be time for tea?

34. I'm right.

a) I'm not right.
b) Am I right?

35. He may be at home.

a) He may not be at home.
b) May he be at home?

36. He used to live here.

a) He didn't use to live here.
b) Did he use to live here?