Hi !!
9) where your father / live
Where does your father live ?
10) what/ sell / Max
What does Mark sell ?
(Do,Does)
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in the interrogative or negative form, the 's' of the 3rd p. singular is added to the auxiliary "do"
Where do you live ?
I live in New York.
Where does he lives?
He lives in LA.
DO takes the 's' of the 3rd p. singular, and the verb stays as a verb in base form.
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hope this helps:)
