Which part of speech is represented by the word "who" in the sentence "Who is listening to the radio?"

In the sentence "Who is listening to the radio?" the word "who" functions as a pronoun. Pronouns are words that take the place of nouns or refer to entities without specifying a name. "Who" specifically is an interrogative pronoun used for asking questions about people. In this instance, it is used to inquire about the identity of the person (or people) who are listening to the radio.

Understanding that "who" is serving to ask a question about a subject highlights its function as a pronoun, distinguishing it from other parts of speech represented in the other answer options. For instance, nouns typically name people, places, or things, adverbs modify verbs, adjectives, or other adverbs, and verbs indicate actions or states of being. Therefore, recognizing "who" as a pronoun clarifies its role in the sentence structure as a substitute for a noun, specifically relating to the identity of the listener.