Working out what happened: must have, can’t have, might have

Examples

1. They must have left before the storm started.

2. She cannot have seen the sign; it was covered.

3. The letter might have gone to the old address.

4. You should have told me before you signed it.

Common mistakes

• ✗Wrong: He must not have known about the meeting.

  ✓Right: He cannot have known about the meeting.

  The confident negative of must have is cannot have, not must not have.

• ✗Wrong: She must knew about it.

  ✓Right: She must have known about it.

  Modals are never followed by a past tense; they take have + participle.

• ✗Wrong: You must have rung me; I was worried.

  ✓Right: You should have rung me; I was worried.

  must have deduces; should have criticises what was not done.

Practice questions

Try each one yourself first, then open “Show answer” for the solution and the reason.

1. 1Choose the correct sentence.

   1. AThe window is broken, so somebody must forced it.
   2. BThe window is broken, so somebody should have forced it.
   3. CThe window is broken, so somebody must not have forced it.
   4. DThe window is broken, so somebody must have forced it.
   Show answer

   Answer: D The window is broken, so somebody must have forced it.

   Evidence now, conclusion about the past: must have + participle.

2. 2Choose the correct sentence.

   1. AShe cannot have written this; the handwriting is different.
   2. BShe could not write this; the handwriting is different.
   3. CShe must not have written this; the handwriting is different.
   4. DShe might not write this; the handwriting is different.
   Show answer

   Answer: A She cannot have written this; the handwriting is different.

   A confident denial of a past event takes cannot have.

3. 3Choose the correct sentence.

   1. AIt might be the wind last night.
   2. BIt might have been the wind.
   3. CIt might had been the wind.
   4. DIt may been the wind.
   Show answer

   Answer: B It might have been the wind.

   An open possibility about the past: might have + participle.

4. 4Fill in the gap.

   Nobody answered, so they _____ out.

   1. Ashould have been
   2. Bmust have been
   3. Cmust be
   4. Dmust have been being
   Show answer

   Answer: B Nobody answered, so they must have been out.

   A conclusion about a past state.

5. 5Fill in the gap.

   He _____ the email; it went to his spam folder.

   1. Acannot see
   2. Bmay not have seen
   3. Cmay not see
   4. Dmust not have saw
   Show answer

   Answer: B He may not have seen the email; it went to his spam folder.

   An uncertain negative about the past.

6. 6Fill in the gap.

   You _____ me. I waited two hours.

   1. Acould have phoned
   2. Bcould have phone
   3. Ccan have phoned
   4. Dcould phone
   Show answer

   Answer: A You could have phoned me. I waited two hours.

   could have + participle criticises the missing action.

7. 7Fill in the gap.

   The keys are in the door, so she _____ home.

   1. Amust have come
   2. Bcannot have come
   3. Cmight come
   4. Dmust come
   Show answer

   Answer: A The keys are in the door, so she must have come home.

   Physical evidence supports a confident conclusion.

8. 8Fill in the gap.

   It _____ easy, but nobody ever said so.

   1. Amust not be
   2. Bmight not be
   3. Ccould not be
   4. Dcannot have been
   Show answer

   Answer: D It cannot have been easy, but nobody ever said so.

   A confident negative deduction about the past.

9. 9This sentence is wrong. Choose the fix.

   Which sentence is wrong?

   1. AThey may not have received it.
   2. BThey cannot have received it.
   3. CThey might not have received it.
   4. DThey must not have received it.
   Show answer

   Answer: D They must not have received it.

   must not have is not used for a confident negative deduction.

10. 10This sentence is wrong. Choose the fix.

    Which sentence is wrong?

    1. AI must have known that at the time.
    2. BI should have known that, but I did not.
    3. CI could have known that if I had asked.
    4. DI should have known that yesterday, so I did.
    Show answer

    Answer: D I should have known that yesterday, so I did.

    should have always means it did NOT happen.