"How many children does she have?"
In this sentence we using the singular word so why we are using of have pls tell me
In the sentence "How many children does she have?", 'have' is functioning as the main verb, and 'does' is the auxiliary (helping) verb, which is the singular form of 'do'.
When, there are both, a main verb and an auxiliary (helping) verb in a sentence, it is NOT the main verb but the auxiliary (helping) verb which agrees with the subject; and the main verb remains in its infinite form.