The correct answer is B) what did you say when you found out that you had won?
The sentence that contains the interrogative pronoun is "what did you say when you found out that you had won?"
An interrogative pronoun is used when we need to ask questions. If we have doubts and want to know something we used interrogative pronouns to know the answer. The interrogative pronouns are "who, what, whom, which." For example: What is under the table? Who is your friend? Whom do you prefer to listen to? or Which one is yours?
