The following is a question from the university entrance examination held in 2013 using the DNC Japan Test.

My brother (  ) have been very popular when he was a high school student. He still gets lots of New Year's cards from his former classmates.

(1) must, (2) ought to, (3)should, (4) would

The correct answer is (1). I wonder why (3)should can't be a correct answer. If must is an answer, should must be another answer, because both must and should have the meaning of necessity.

  • Ven I'm guessing is your way of saying V (erb) and the suffix -en, but that would exclude most verbs that are either regular or have different suffixes e.g. "She must have played well, if she won the tournament.” and "He says he's lost his glasses, but he must have put them somewhere.” It's must / should + have + PP (past participle)
    – Mari-Lou A
    Commented May 2, 2021 at 12:41
  • @Mari-LouA, thank you. I am glad to have your comment again. This is the first time in (perhaps) three years that I have posted my question to this site.
    – Aki
    Commented May 2, 2021 at 12:59

1 Answer 1


"Both must and should have the meaning of necessity" - but must have and should have have different meanings.

He must have been very popular = It's extremely likely that he was popular.

He should have been very popular = It seemed likely at the time that he would be popular (with the expected continuation ...but in fact he was not.)

  • thank you for your help. So, "must have +(past participle)" means a deduction based on current evidence, and "should have + (past participle)" means a deduction in the past based on evidence at the time. Am I right?
    – Aki
    Commented May 2, 2021 at 13:11
  • 1
    Yes, that's right - though perhaps an expectation in the past rather than a deduction. Commented May 2, 2021 at 13:50
  • @Kate Bunting I'm not sure that is quite it. 'Must have" is, interestingly, the opposite not of 'mustn't have' but of 'can't have'. So yes, 'extremely likely' but with a feeling of 'surely it can't have been otherwise'. 'should have been' often means 'ought to have been' as in "Caruthers should have been head boy <but Grabber Major got it because his Dad gave money for the new chrcket pavillion>."
    – Tuffy
    Commented May 2, 2021 at 18:08

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