the answers was marked wrong in English as "the family cat is black" but it IS the most common expression in English. You don't generally say the familys cat is black, we would say the family cat is black or if its about someone else then we would more likely say "their family cat is black".
"Ailenin kedisi siyah." Translation: The family's cat is black.
why is the family cat is black wrong ? It's OK In English although I guess it's doesn't show possession ?
Aile - family - (adjective)
The family cat is black. - Aile kedisi siyah.
You answered your own question. You have not used the genitive case suffix of possession (n) "-in." It is in the Turkish question?
Ah! but no. You mean Duolingo hasn't used the genetive case. I was writing the answer to the sentence in English. I was saying that the phrase the family cat is black is as acceptables as the family's cat is black though there is a subtlety. In the first sentence family is an adjective so I suppose the former answer is wrong in the strict sense of the question