We know from earlier Hints that could has several different
uses in present or future time, that could also shows ability
in the past, and that could has a past form, could have,
which is followed by the past participle of the main verb:
The could have form is also used in "if" sentences to show
unreal conditions in past time. Conditional sentences of
this kind refer to hypothetical, impossible, contrary-to-fact,
unreal situations. In them, could have shows a possibility
that didn't happen.
Examples:
You could have asked for help if you had wanted to.
(It was possible for you to ask for help, but you didnt want to.)
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If Julia had had enough money, she could have bought a car.
(It wasn't possible for Julia to buy a car because she didn't
have enough money.)
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Julia could have made a down payment on a car if she
hadn't paid so much money for her new computer.
(It wasn't possible for Julia to make a down payment on
a car because she paid too much money for her new computer.)
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Special Notes:
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Remember that could have is used to show
possibility in the past. It is not used to show
past ability or past permission. |
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2. |
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To show past ability in unreal conditional sentences,
use had been able or would have been able:
I would have helped you if I had been able to.
(I didn't help you because I wasn't able to.)
If he had had enough time, he would have
been able to do a good job. (He wasn't able
to do a good job because he didn't have enough time.)
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3. |
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To show past permission in unreal conditional
sentences, use had had permission:
I would have left early if I had had permission.
(I didn't leave early because I didn't have permission.)
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