"František could not drink."
Translation:František nesměl pít.
I agree with others that, based on the ENGLISH sentence, there is no way, absent context, to know which interpretation of "could" would be appropriate for the Czech translation. I got this as a Mark the Correct Meaning exercise, but if it had been a Write This in Czech exercise instead, I don't think I would have used "smět" for the verb. Maybe all of the reasonable verb possibilities should be accepted, if that would not mess things up in the reverse translation...
UPDATE ----- I've changed my mind about this. Given that this skill uses "smět" repeatedly, the skill itself, in a way, provides the necessary context. So I take back my earlier suggestion!
If the sentence is presented without additional info, it could well be translated by "František neuměl pít". The fact that is "accepted", however is only due to the fact that the words differ only in one letter. I think "František was not allowed to drink" is a far better translation for "František neuměl pít", btw. (smít is German "dürfen", which usually translates to "may" in most contexts).
I am afraid you got it mixed up. Frantisek was not allowed to drink means that for some reason he was banned from drinking. František neuměl pít means that he did not know how to drink. Either we refer to his inability to handle alcohol or maybe he was a baby and did not know how to use a glass. In other words, he could not drink.
When we ban František from drinking (he has a surgery in an hour to avoid the alcohol topic) it would be František nesměl pít.