"I do not take your shirts off."
Translation:Ní bhainim bhur léinte díbh.
I got this question as an English to Irish translation and there is no way for me to tell if the "you" in this sentence is singular or plural. Obviously with more context, this wouldn't happen, but why was I marked incorrect for using the singular 'you' instead of the plural?
I have found that I get more out of Duolingo by trying to give the answer they want me to give rather than by getting them to accept my answer. In this question, they are trying to get us to practice using "bhur" and "dibh." The sentence could be interpreted different ways, but then you don't get the practice they're trying to give you.
Both “take off” and bain de are phrasal verbs. The final “you” in English isn’t necessary, but such a sentence is ambiguous, since it wouldn’t identify which people are currently wearing those shirts. The pronoun would be needed in Irish, though; thus, it wouldn’t be ambiguous in Irish. Therefore, for the given ambiguous English sentence, any Irish prepositional pronoun form of de could be a valid translation; díbh would be the likeliest choice, but given the lack of context, it wouldn’t necessarily be what was meant.
Strictly speaking, all present tense verbs are negated with ní, but in the case of tá, the dependent form fuil is used after particles like an (an bhfuil) and ní but ní fhuil has fused to níl, so, as you say, níl is the negative of tá, but it just a special case of ní, and because that verb is so much more common than any other verb, níl crops up a lot.
It's ambiguous - one can't tell who is wearing the shirts without more context.
Eclectic1234 says we should just try to give the answers they are looking for, but the student won't know what that might be until they guess, possibly get it wrong, figure out what Duo was looking for, then remember the next time it comes around - the hard part for me!
Doesn't the application of lenition also depend upon the cause of lenition as well? For example "d" is lenited after uile (gach uile dhuine) but not after an or sa (an-dorcha, sa dorchadas), for example? This has led to me being confused on a number of occasions - just when I thought I was getting the hang of it!