Note the speaker sounds like he's saying "an gù mòr", rather than "cù". That's a phenomenon called eclipsis. Here's a little article on it: https://gaelicgrammar.org/~gaelic/mediawiki/index.php/Eclipsis
So is this speaker a speaker of a different dialect? He seems to pronounce both "c" (an cat, an cù) and "t-" (an t-each) without aspiration after "an", whereas I thought other speakers aspirate these consonants. Or do all Gaelic speakers omit the aspiration after the article "an"? If this is a dialect issue, then what dialect is he speaking?
Might be an oversight on the contributors’ part – you know, they are volunteers and humans too, might not have anticipated every possible answer to every single question. If so, it is worth reporting as a missing correct translation using the Report button under the exercise.
But then you might have some other mistake in your answer that you missed.
Yeah, it's a bit confusing, because ann is a little weird as prepositions go; "ann an"/"ann am" is the indefinite "in a" - the "an/am" is not a "the" here, it's just a particle attached to the "ann".
The definite form of ann, as in "in the", is "anns an". We'll see more of this when the course covers more of the dative/prepositional case, which makes some subtle changes to feminine nouns.
Upvoted, good answer. I’ll just add my minor two cents, hope you don’t mind:
It’s not even in a – there is no indefinite a in Gaelic. Ann an just is the default form of in (eg. there’s no a in ann an Glaschu in Glasgow).
Historically the preposition was just an (and apparently you still can just say an Glaschu for in Glasgow) and the ann part was probably added a few centuries ago by native speakers to disambiguate from the definite article an – which ironically now causes a lot of confusion for learners ;-).
Re: anns – yes that’s the form before the definite article, I’ll just add that an in anns an is the definite article and eg. before plurals you get anns na. So it’s the whole ann an that changes to just anns.