"Do you drink milk?"

I am wondering about this as well.

"Ты" is singular. "Вы" is plural, or formal.

I know Duolingo lesson's are not perfect, but, it's free, and when I have a question before answering, I click on a browser tab and Google search the answer like: how do you say You drink milk in greek, for instance. Or, I just just enter gibberish for Duolingo to show the the anwer: Then I cut and past the answer in my notebook so that when Duolingo asks me again (and Duolingo always asks a failed question again), then I will have the answer. Since a Duolingo language tree can't possibly, "teach" every conjugation, inflection, etc., I use topics to search for the answers on Google Search, such as how do you say: I drink milk, etc, how do you say He drinks mik, they drink milk. Sometimes when I can't figure it out asking Google, I come to the discussions and read previous comments, questions and answers, and that helps. I know Duolingo is not a comprehensive language learning platform. But, I am using it as a starting point which helps me to know what questions I need to ask on the internet, and on youtube. My goal, learn languages without ever having to pay for a book or specialized program. Thanks!

i picked two answers ты and Вы sometimes you can choose two answers it says Mark ALL correct translations

These are different conjugations of the same infinitive, пить.

Ты пьёшь

Он/она/оно пьёт

https://en.openrussian.org/ru/пить

Your screenshot says, "Correct solutions." You must choose both Вы пьёте молоко? and Ты пьёшь молоко in order to be marked correct. In English, both sentences would be phrased, "Do you drink milk?" There is only one way to say this in English, and there are two ways to say it in Russian. I hope this helps. Let me know if you have further questions.