Must Have, Might Have, Can't Have — Exercises
Practice modals of deduction about the past: it must have rained, I might have left them at work, she can't have been there.
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The streets are all wet. It ___ rained during the night.
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must have
A confident guess about the past → 'must have' + past participle ('must have rained'). 'Had to' is about obligation, not guessing.
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I'm not sure where my keys are. I ___ left them at the office.
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might have
A possibility about the past ('I'm not sure') → 'might have' + past participle. 'Might left' and 'must left' are not possible forms.
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Tom ___ seen us — he walked straight past without saying hello.
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can't have
You're sure something did NOT happen in the past → 'can't have' + past participle. 'Mustn't have' is not used for guesses.
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The house is completely dark. They ___ gone to bed already.
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must have
A confident guess about something that has already happened (the dark house is the evidence) → 'must have gone'. 'Mustn't have' is never used for guesses, and 'had to' is about obligation.
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Kate ___ been at the party last night — she was in hospital.
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can't have
She was in hospital, so you're sure she wasn't at the party → 'can't have been'. Guesses never use 'mustn't'.
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I've texted Mia three times and she hasn't replied. She ___ have seen my messages yet — her phone's been off all day.
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can't
Her phone has been off all day, so you're sure she hasn't seen them → 'can't have seen'. The negative guess is 'can't have', never 'mustn't have'.
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Someone's been in the flat
Ella: Jack, did you leave the kitchen window open this morning?
Jack: No, I definitely closed it. Why?
Ella: It's wide open now, and there's a cup of coffee on the table that wasn't there this morning. Someone {1} been here — I'm sure of it.
Jack: Well, it {2} be Tom. He's in Spain until Friday.
Ella: Then who? Nobody else has a key.
Jack: Your mum has one. She {3} dropped by with those plants she promised you — I'm not sure.
Ella: Maybe. But she {4} called first. She knows I hate surprises.
Jack: Is the coffee still warm?
Ella: Yes, it's hot. She {5} left long ago.
Jack: {6} I give her a ring?
Ella: Yes, please. Oh, wait — there's a note under the cup: 'Brought the plants. Love, Mum.'
Jack: Well, you {7} worried, then!
Ella: I know. I {8} panic like that again — I promise.Show answer
1. must have — Ella is sure ('I'm sure of it') that someone came in earlier → 'must have been'.
2. can't — Tom is in Spain, so Jack is sure it isn't him → 'it can't be Tom'. Negative guesses use 'can't', never 'mustn't'.
3. might have — Jack isn't sure ('I'm not sure') → a possibility about the past: 'might have dropped by'.
4. should have — Her mum didn't call, and Ella thinks she ought to have → criticism: 'should have called'.
5. can't have — The coffee is still hot, so Ella is sure her mum didn't leave long ago → 'can't have left'.
6. shall — Jack is offering to do something → 'Shall I give her a ring?'
7. needn't have — Ella did worry, and it turned out there was no reason → 'needn't have worried'.
8. won't — A promise not to do something again ('I promise') → 'won't': 'I won't panic like that again'.
Must Have, Might Have and Can't Have: Guessing About the Past
To make a guess about the past, use the same modal verbs as for the present and add have + past participle. Must have expresses a confident conclusion: The streets are wet — it must have rained during the night. Might have, may have and could have express a possibility: I'm not sure where my keys are — I might have left them at the office. Can't have and couldn't have express a confident negative conclusion: Kate can't have been at the party — she was in hospital. The modal itself never changes form, so must left and might rained are impossible; the past is carried entirely by have + participle. A common confusion is between must have left (I think she left) and had to leave (she was obliged to leave). The first is a deduction made now about the past; the second reports a past obligation.
Last updated: · Satori Editorial