Could+past participle


Are the following sentences grammatically correct?

1. How could it have run out?
2. How can it have run out?

I am 99.9% sure that #1 is correct but the usage of "can" in sentence #2 makes me a little bit uncertain although i think that i may be correct as well.
  • Loob

    Senior Member
    English UK
    You are right, #1 is correct. In the case of #2 "have" is not grammatically correct and should be deleted.
    I'm sorry, thegreathoo, you're wrong about #2.:(.

    "How can it have run out?" is perfectly grammatical.
    A. The paper's run out.
    B. How can it have run out? I put more paper in the machine only an hour ago


    Senior Member
    English - England
    Yes, these forms are all common:
    He would have done.
    He could have done.
    He might have done.
    He should have done.

    expresses past tense. Would could, might and should, contrasting with will, can, may and shall, suggest essentially that the statement is conditional, tentative, subjunctive etc.
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