In the challenge where we ask you to translate this sentence, you can tell that this is plural, since "ils" and "sortent" are 3rd person plural.
In the challenge where we ask you to listen to this sentence and type it in French, you can tell that this is plural, because "sortent" (3rd person plural) is pronounced differently from "sort" (3rd person singular).
You can practice with those links:
I'd like to point out that in (British) English, dinner can be either in the evening or at midday. According to my dictionary, in many French speaking countries and in several parts of France dîner can also refer to the lunchtime meal.
I realise that this is a difficult issue of when the translations need to be either more precise or more natural... The problem is that the user has no way of knowing which one Duo wants e.g. when to type "the female cat is eating," rather than the (much more natural/likely) phrase "the cat is eating).
Either way DuoLingo is a fantastic resource, so many thanks to all involved.
That doesn't mean it shouldn't be accepted though. A French person might say in English "We're going out to eat", even when she is referring to dinner. Does that mean she is wrong?
An extreme example would be to think that Eskimos have a dozen different words for different kinds of snow. Is it wrong therefore to translate all of those words, in English, as simply "snow"?
Scroll down for the sentences at this site. https://dictionary.reverso.net/english-french/They+left+the+dinner
Well, it is tricky because you don’t mean “leave dinner out for someone”, but actually to leave from the place where dinner is being held. In French that would be “partir de” or if you mean that you leave during dinner before it was done, than you could use “quitter”.
« Il sort » sounds similar, but the final ‘t’ is not pronounced in the singular and « Ils sortent » will pronounce that first ‘t’. So, you can tell plural for this verb, but there are other verbs that don’t have a difference in sound from singular to plural. In those cases, Duolingo usually accepts both as correct when the words are not spelled out in the Listen to Spanish and write it down in Spanish exercise. In some cases, the homonyms need to be reported to allow both to be accepted for that exercise.