"An toil leat marag-dhubh? Cha toil."
Translation:Do you like black pudding? No.
tha toil with the meaning of liking something isn’t a correct phrase anywhere. If it’s accepted it’s because Duolingo treats typos too liberally and decides that tha is close enough to cha – which in Gaelic are completely different words (they are two entirely different forms of two entirely different verbs!¹). Unfortunately nothing Gaelic course volunteers can do about – the software just accepts one letter difference and doesn’t even warn about it.
¹ tha is positive form of the bi verb, cha(n) is the negative form of the copula is (and also the general negative particle); only the copula is is used in the phrase is toil le X…, cha toil le X…, an toil le X…? for X likes / does not like… and does X like…?.