Deduction About the Past — Must/Might/Can’t Have

You come home and find a broken window. What probably happened?

Notice

  • Someone must have broken in. (confident guess about the past)
  • It might have been the wind. (possible)
  • It can’t have been my brother, he wasn’t here. (confident negative)

Rule

For guesses about the past, add have + past participle: must have (confident guess it happened), might/could have (possible), can’t have (confident it did NOT happen). The form doesn’t change for the subject.

Practice

  1. The ground is wet — it ___ (must) have rained.
    Answer: must have rained
  2. She looks upset — something ___ (might) have happened.
    Answer: might have happened
  3. He ___ (can’t) have forgotten, I reminded him twice.
    Answer: can’t have forgotten
  4. They ___ (could) have missed the bus.
    Answer: could have missed
  5. The light was off — he ___ (must) have gone to bed.
    Answer: must have gone

Connect

Fix mistakes in past-deduction sentences like these.

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CEFR: Spoken Production — speculate about past events with connected phrases.

Azizul Hakim
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