Must Have, Might Have, Can’t Have
I can mark different strengths of inference about a past event.
Try the activities, then check your answers.
Try the activities, then check your answers.
Choose a short recording.
Start with the contrast
The meeting room is empty and all the bags are gone. “They must have left,” says Jo. “They might have gone for lunch,” adds Mina. The camera shows Ben elsewhere at the relevant time: “Ben can’t have opened this door then.” These are interpretations of evidence.
Read the situation transcript
The meeting room is empty and all the bags are gone. “They must have left,” says Jo. “They might have gone for lunch,” adds Mina. The camera shows Ben elsewhere at the relevant time: “Ben can’t have opened this door then.” These are interpretations of evidence.
Does must have left describe an obligation to leave?
Compare your idea
No. Here it expresses a strong conclusion about a past event.
How it works
Use modal plus have plus a participle for past inference. Must have presents a strong conclusion; might have presents a possibility; can’t have presents a conclusion that something was not possible.
The speaker’s confidence is not proof. State the evidence and avoid arbitrary certainty percentages. Must have in this pattern differs from had to, which can describe past obligation.
Must/might/can’t + have + past participle.
Notice this
They must have left.
The speaker draws a strong positive conclusion.
Compare this
They might have gone for lunch.
This is offered as one possibility.
Hear the examples
They must have left.
The speaker draws a strong positive conclusion.
They might have gone for lunch.
This is offered as one possibility.
Ben can’t have opened it then.
The speaker rules out that past possibility.
She had to leave early.
This describes past obligation, not the same inference.
One mistake worth avoiding
Instead of: He must has forgotten.
Say: He must have forgotten.
After a modal, use have, not has.
You say
Hear the prompt, answer aloud, then deliberately reveal or hear one possible model. Check it and retry with a changed detail.
Your turn 1
Make a cautious explanation for an empty room.
Compare a possible model
Reveal the model text
They might have gone outside.
Check yourself: Use possibility without claiming certainty.
Retry with one detail of your own. Other wording is welcome when it meets this check.
Your turn 2
Draw a strong inference from an invented clue.
Compare a possible model
Reveal the model text
The floor is wet; someone must have cleaned it.
Check yourself: Acknowledge that an inference is not direct proof.
Retry with one detail of your own. Other wording is welcome when it meets this check.
Your turn 3
Rule out a possibility using supplied evidence.
Compare a possible model
Reveal the model text
Ben can’t have taken it; he was elsewhere at the time.
Check yourself: The evidence must actually relate to the conclusion.
Retry with one detail of your own. Other wording is welcome when it meets this check.
Two guided self-checks
Say or write your answer before opening a model.
Self-check 1
Complete: She might have ___ the message. Use miss.
Compare a model and explanation
She might have missed the message.
Use the participle after have.
Self-check 2
Change past obligation to a distinct inference: She had to leave early. Say you conclude she left.
Compare a model and explanation
She must have left early.
The new form changes the meaning from obligation to inference.
Check your understanding
Choose one answer to each question, then check your answers. One of the ten questions is listening.
Automatic scoring needs JavaScript. Use the answer key after attempting all ten questions.
Answer key with explanations
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He must ___ forgotten the time.
have: A modal is followed by have in this perfect pattern.
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They might have ___ outside. Use go.
gone: Use the participle gone after have.
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Which form presents only a possibility?
Might have left: Might have offers a possible past explanation.
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What does “must have left” normally express in this inference task?
A strong conclusion about the past: The perfect modal is epistemic here, not an instruction.
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Choose the form that rules out a past possibility.
Can’t have taken it: Can’t have presents the speaker’s negative conclusion.
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Correct “She may has missed it.”
She may have missed it.: Use modal + have + participle.
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Does strong confidence make an inference infallible?
No: A strong inference can still turn out to be mistaken.
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How certain is the speaker’s explanation of the missing keys?
It is one possibility.: Might have left them in the car marks a possible explanation.
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Which sentence describes past obligation rather than deduction?
He had to leave early.: Had to can express a past requirement; the perfect modals here infer an event.
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What three distinctions matter here?
Strong conclusion, possibility and ruled-out possibility: The forms express different stances toward a past explanation.
Take it with you
I can mark different strengths of inference about a past event.