- If A is bigger than B, and B is bigger than C, then A must be bigger than C.
Mary keeps crying. She must have some problem.
There’s the doorbell. It must be Roger.
‘I’m in love. ‘ ‘That must be nice.’
- ‘There’s somebody at the door. Who can it be?
It can’t be the postman. It’s only seven o’clock.’
What do you think this letter can mean?
- (can have in questions and negatives).
[must/can/can’t have + past participle]
‘We went to Rome last month.’ ‘That must have been nice.’
I don’t think he can have heard you. Call again.
Where can John have put the matches? He can’t have thrown them away.