Because niño is a boy. If it said niña, it would be a girl. While I do understand your answer, it isnt as if you tried to say ellos when duolingo wanted ellas.
Hey i typed el nino quiere dibijar in perro without the tilde on the n in nino and i still got this wrong.
I imagine youre talking abot how that wad rejeced as a translation... This is a language class and expecting it to accept every single form of slang is insane. I get it if they didnt accept "mum" instead of "mom" (since both are said, depending on where you live).