Which among the following sentences contains an interrogative pronoun?

The correct option is B) ‘Where are you going?’. The words that are used in place of a noun are pronouns.  The name of a person, place, animal, or item can be the noun that is replaced. Pronouns that are used to ask questions are called interrogative pronouns. In the given statement, ‘Where are you going?’,  the pronoun ‘where’ is an interrogative pronoun. In the other three options no interrogative pronoun such as what, where, who, when, etc. can be observed; hence making option (B) the required answer.