"Bois-tu du lait ?"
How do you distinguish between 'Do you drink milk?' (i.e. ever) or 'Are you drinking milk?' (i.e. right now). Both are 'correct' answers according to the question...
In French there is no equivalent tense to the present progressive in English. We translate both "Are you drinking milk?" and "Do you drink milk?" into "Bois-tu du lait?". In colloquial French, we sometimes use the expression "en train de + INFINITIVE VERB" to express the idea "progressive" tense. For example, you can translate "Are you drinking milk?" into "Es-tu en train de boire du lait ?"
You have to add a hyphen between the verb and the subject, when the verb comes on first position (best level of language):
e.g. "Bois-tu du lait ?" ("Do you drink milk?)
Do not use a hyphen if the subject comes first (more colloquial):
e.g. "Tu bois du lait" ("You drink milk?")