Grammar Practice in Context - David Bolton, Noel Goodey 1997
28 Must, can’t Must have done, can’t have done
Quick reference
We use:
• must + infinitive without to or must be + -mg when we feel certain something is true.
He must live here. That’s his car outside. The television's on. He must be watching TV.
Note the short answers.
Is he in? - He must be.
Does he know we’re here?-He must do. I told him we were coming at 8.00.
• can't + infinitive without to or can't be + -ing when we think something is impossible.
She’s just lost her job. She can’t have much money. She can’t be feeling very happy.
• must have + a past participle or must have been + -ing when we feel certain something was true in the past.
The video's disappeared. Burglars must have taken it. They must have been watching the house when I went out. - Did they get in through a window? - They must have done
• can't have + past participle or can’t have been + -ing when we think something was impossible. He hit a motorcyclist. He can’t have seen him. He can’t have been watching the road.
Was he driving carefully? - He can’t have been.
1 Claire has got a maths exam soon. Her parents are talking about her. Complete the second sentence so that it has a similar meaning to the first, using the word(s) given.
Example: I’m sure it’s a difficult time for her. (must) It must be a difficult time for her.
’I’m sure she’s feeling worried.’ (must) (1) ... worried.
’Do you think she’s feeling nervous?'
’I’m sure she is.’ (must) (2) ... be.
’I'm sure she isn't sleeping well.' (can’t) (3) She ...
'I don’t suppose she likes all this hard work.’
'I’m sure she doesn’t.' (can’t) (4) ... do.
’I’m sure she thinks she’s going to fail the exam.' (must)
(5) She ... to fail the exam.
’Yes, I’m sure that's the problem.’ (must) (6) Yes, that ...
’But she’s good at maths. I’m sure she knows that.’ (must) (7) She ... that.
’I'm sure she isn’t feeling very confident, that’s all.’ (can’t)
(8) She ... very confident, that's all.
After the maths exam Claire comes home, looking miserable. Her parents are talking about her again.
'I’m sure the exam was difficult.’ (must have) (9) The exam ... difficult.
’It looks as if she didn’t do very well.’ (can’t have) (10) She ... very well.
2 Andy Caswell has been shopping in town. He is talking to his wife, Jenny. Complete the sentences, using must have or can’t have + past participle, or must have been/can’t have been + -ing.
Andy: I bought myself a new mobile phone. It’s one ol the best you can buy. Look!
Jenny: (I be) It ... expensive.
Andy: No, I got it at a special price.
Jenny: Well, it (2 be) ... cheap if it’s the best you can buy. (3 cost) It ... at least £200!
Andy: Well, nearly. By the way, I think I’ve lost my credit card. (4 drop) I ... it somewhere. But I had it when I bought the phone.
Jenny: Well, (5 leave) you ... at the shop.
Andy: (6 leave) I ... it there, because I used it to buy some petrol on the way home. Oh, I forgot to tell you, I had a small accident in the car. I hit a tree.
Jenny: (7 damage) You ... the car. (8 go) You ... too fast.
Andy: No, I wasn’t going fast.
Jenny: Well, (9 concentrate) you ...
Andy: No, I was concentrating. I was trying to ring you on my new phone.
3 The police are looking for Meg Sharp. Look at the pictures, and make your conclusions. Answer the questions, using the short answers: She must have been/She must have done. She can’t have been/She can’t have done.
1 Did she take her car?
2 Was she planning to be away for a long time?
3 Was she feeling well?
4 Has she gone abroad?
4 Think of an important time in the past. Imagine how people felt and make deductions. Write three sentences using must have + past participle.
Example: They must have been very excited.
Write three sentences using can't have + past participle. Example: They can't have had much to eat.
Check your answers with a teacher.