"Practical English Usage" 不错

zyc50

I found this from my book, \"ractical English Usage\" b M.S., 3rd edition

359. must(2): deduction
(concluding that something is _certain_)
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4. That must have been nice
We can use _must have + past participle_ to express *certainty* about
the past.
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_Can_ is used in questions and negatives.

-- Where can John have put the matches? He can't have thrown them away.