why use are you why not do you ?

We use both.But it depends on sentence what type of sentence that is.We use "do" as well as are in simple present tense. Do - with I,we,you,they, plural subject in simple present tense when there is a verb in the given sentence. For ex:- Do you teach in that school? Are - with we,you,they, plural subject in simple present tense when there is no verb in the given sentence. It's also used in present continuous tense with v4( ing form verb). Ex:- Are we teachers? They are teaching in that college.

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