They ought to have finished working by now.
Carlos may have fixed his car if he had had the chance.
She might not (may not) have come if she had known it would snow.
I should have called you before I left.
He must have seen the Statue of Liberty. He came to New York by ship.
He could have driven himself to work today.
Possibility / Ability
Possibility
Deduction
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Advisible
Possibility