The correct answer is “indefinite pronoun”. An indefinite pronoun refers to a non-specific person or thing. As any other pronoun, it substitutes a noun. Their biggest matter is determining whether they are singular or plural. Examples of it can be “everything” as singular, “both” as plural and “some” that can be singular or plural. In the phrase is clear that the speaker is not referring to someone in particular, he just speaks in general.
