Which of the following is NOT a relative pronoun?

The answer is correct because "I" is not a relative pronoun; rather, it is a personal pronoun that refers to the speaker. Relative pronouns, on the other hand, introduce relative clauses and relate to a noun previously mentioned in the sentence. They provide additional information about that noun.

In this context, "that," "whom," and "which" all serve to connect clauses, referencing people or things to add detail or clarification. For instance, "who" and "whom" relate specifically to people, while "that" and "which" are used for things or non-human entities. Understanding the function of relative pronouns helps in constructing clear and informative sentences, while recognizing personal pronouns like "I" enables proper subject usage in writing.