I don't understand why both are correct answers. Isn't it supposed to use [be able to] rather than [could] if the situation is a specific event in a specific moment, which I think is this case? For example, be able to is correct, not could, in this sentence : We [were able to] finish the football match before it started snowing too heavily.

By the way, this is a question from Advanced grammar in use. Please let me know what I am missing. Thank you.

  • Who told you that you must use be able to rather than can/could if it’s a specific situation in a specific moment? There is no such rule. Can/could fulfils several epistemic roles relating mainly to ability, habituality, evidentiality and permission; this makes it ambiguous in many cases. Be able to is less ambiguous, since it deals exclusively with ability, so of course there are cases where be able to is generally preferred or more common – but there is no rule saying that it must be used in any situation, except with untensed forms (which can/could does not possess). Apr 22, 2019 at 16:27

2 Answers 2


Let's say the rebels had convinced 20k soldiers that their cause was a noble one but told them to not say anything and just continue to pretend to be loyal soldiers. In this case, the rebels could draw on the support of over 20,000 soldiers, but choose not to.

Later, perhaps, during a battle which they were losing, the rebels were able to draw on the support of over 20,000 soldiers and thus emerged victorious.


Could is a conditional and past tense indicator of can so therefore,

Could means both "were able to" and "would be able to"

I believe your confusion is involving the unique dual tense usage of this verb.

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