"O garoto janta."
Tradução:Il ragazzo cena.
Bambino is like a child (between 5-12 years) while ragazzo (your menino) starts to become more adult (from 13-18 more or less) so as sentence itself is correct but for duolingo would be wrong.
Ok Feliksia! Thanks for the explanation of the difference between Bambino and Ragazzo (I didn't know). But "Menino" (a) is used almost exactly as Bambino, "Menino" is for a Child and not a teen (in the actual use), we can use informally "Menino" for everybody using sense of humor, and the dictionary says that we can use menino for an adolecent, but nobody uses it (at least in Brazil), teens are at that stage that they want to be considered young... I'd use Menino or menina for someone that is from 4 to 13... But thanks very much for your help... :)
Oh gosh, and i always thought that menino is a boy xD...so garoto is a boy, there is always something to learn every day xD :o!