Should / ought to / must have + past participle

The structure should / must / ought to have + past participle is used to say what one thinks was essential.

  • You should have locked the door before leaving the house. (= You did not lock the door before leaving the house, though that was very important.)
  • They should not have raised the price of essential articles. (= They raised the price of essential articles. That was not right.)
  • He must have been more careful. (= He wasn’t careful though that was absolutely necessary.)
  • He ought to have finished the job last week. (= It was absolutely necessary for him to finish the job last week, but he failed to do so.)

Read the following statements. The first is a statement. The second is a response to it.

  • I didn’t thank him.
  • You should have thanked him.
  • He didn’t ask me before borrowing my car.
  • He should have asked you before borrowing your car.
  • I told him a lie.
  • You ought not to have told him a lie.
  • She behaved rather rudely.
  • She ought not to have behaved rudely.
  • He forgot to bring his passport.
  • He should not have forgotten to bring his passport.
  • The man was under the influence of alcohol.
  • The man should not have been under the influence of alcohol.
  • The boy was rude to the old man.
  • The boy must not have been rude to the old man.
  • He did not prepare for the test.
  • He ought to have prepared for the test.
  • She took the matter too seriously.
  • She should not have taken the matter too seriously.

Notes

Must is stronger than should. Ought to is similar to should. It is not as strong as must.

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