"I like the black" is not good english it should be "I like black." if referring to the colour or "I like the black something" e.g. book, dress, etc.
duolingo requires you to use "the" even if it is choppy and bad english
Looks like they just corrected it :)
Yeah, I agree.
In English: Which one do you want, the black one or the red one? I like the black.