Past modal verbs of deduction

Past modal verbs of deduction

Exercise 2

Choose the correct option to complete the sentences below.

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1 I'm sorry but Mr. Banks isn't here. He _______ left.

A.can't have

B.might have

C.must have

D.should have

2 We really enjoyed the movie. You _______ come with us.

A.might have

B.can't have

C.must have

D.should have

3 They _______ bought a new house. They are both unemployed.

A.can't have

B.might not have

C.mustn't have

D.could have

4 He didn't study at all and passed the exam, so he ________ cheated.

A.can have

B.must have

C.ought to have

D.might have

5 My car isn't there anymore! It _______ stolen while I was shopping.

A.couldn't have been

B.should have been

C.mustn't have been

D.might have been

6 You _______ broken up with her; she was perfect for you.

A.shouldn't have

B.couldn't have

C.mustn't have

D.might have

7 He _______ killed him, but we need more evidence.

A.can have

B.must have

C.might have

D.should have

8 Alex _______ studied very hard, because she got top marks in all the exams.

A.can't have

B.might have

C.should have

D.must have

9 'I can't find my keys.' 'Have you checked in your car. You _______ left them there.'

A.can't have

B.might have

C.should have

D.can have

10 We _______ bought enough beer for the party.

A.shouldn't have

B.must not have

C.ought not have

D.may not have

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Past modal verbs of deduction: Grammar chart

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Modal verbs of deduction and speculation

We can use some modal verbs + an infinitive to talk about how certain we are that something is or is not true. We can also use some modal verbs + have + past participle to talk about how certain we are that something was or was not true in the past.

Must have done

We use must have + past participle to say that we are quite sure that something was true or happened in the past.

• I can’t find my wallet! I must have dropped it in the taxi.
• You must have had a real scare when you saw the crocodile. 

Can’t have done

We use can’t/couldn’t have + past participle to say that we are quite sure that something did NOT happen or was NOT true in the past.

• You can’t/couldn’t have seen John last night. He was in hospital. 
• She can’t/couldn’t have passed the test. She didn’t even open the books. 

❗ Note that for negative deduction, we use can’t (NOT mustn’t)

• He mustn’t be that famous.
• He can’t be that famous.

Could/might/may have done

We can use could have + past participle to say that something was possible in the past or someone had the possibility to do something but didn’t do it.

• You could have called me to say you weren’t coming. I waited for hours. 

We can also use could/might/may have + past participle to say that it’s possible that something was true or happened in the past.

• It’s been three days. They might/may have finished painting the house by now. 
• If they left at 9, they might/may have already arrived.

❗ Note that we use might not or may not (NOT could not) to talk about a negative possibility.

• She might/may not have heard us. Knock again. 

Should/ought to have done

We use should have/ought to have + past participle to talk about a situation expected to happen in the past. This form is normally used for criticism.

• You should/ought to have already packed your things. We’re going to be late. 
• He should/ought to have studied more. Nobody fails if they study.