how do i know to use "du"?
Was there any way i was supposed to know that the "You" was plural?
Now you know... the English "you" is translated either by "tu" (someone you know well), or "vous" (someone you don't know) or "vous" (several persons).
What was wrong with "Tu bois du vin?"
You may report it.
"Nous avons besoin de pain", "tu bois du vin".
Why du in one case and de in the other?
Why not tu bois du le vin?
In masculine, "du" is the contraction of "de" + "le", and it is an article in itself.
In feminine, "de la" does not contract.
Whenever the next word starts with a vowel sound, "du" and "de la" are changed to "de l'".
Why not vous boivez du vin?
Could this be an acceptable answer? Duolingo does not accept it!
Je bois, tu bois, il/elle/on boit, nous buvons, vous buvez, ils/elles boivent.