I'll ask you one last time. Who is Sponge Bob?? Interrogative Pronoun is a pronoun that introduces a question. These interrogative pronouns are who, whom, which and what . The additional set of these Interrogative pronouns are there compound forms with suffix 'ever;' whoever, whomever, whichever and whatever . These words become Interrogative pronouns more as a function than a separate category as they may also be used in other Kinds of Pronouns. In this regard, let us concentrate in learning how these words are used as Interrogative pronoun. Let us study this chart to see how each word are used in a sentence.