"The boy drinks the milk."
Translation:De jongen drinkt de melk.
native dutch and english speakers here it is just like spanish with le and la and there are no rules you just have to learn them and listen which on sound the best .
Duolingo should offer some Grammer explanation, it repeats always the same frases but without explaining why.... Here the difference is that it is not the article but a frase and milk is the object of the frase. Het milk.... Ik drink de milk