What is an interrogative pronoun?
An interrogative pronoun is a pronoun that is used to introduce a question. The main English interrogative pronouns are what, which, who, whom, and whose.
They can be used in a direct question, which ends in a question mark (e.g., ‘What is your favourite color?’) and indirect questions, which don’t have a question mark (e.g., ‘I asked what her favourite color was’).