Which relative pronoun correctly starts a clause describing the author who wrote the book?

• A. who
• B. whom
• C. which
• D. that

Answer: (A)

When a clause describes a person and the person is the one doing the action, the pronoun that starts the clause should be who. In the phrase describing the author, the author is the one who wrote the book, so the relative clause needs a subject pronoun for the verb wrote. That’s why who fits perfectly: it acts as the subject of the verb in the relative clause.

So, the correct choice makes sense in the sentence: The author who wrote the book. Using whom would put the author in the object position (the author whom someone wrote), which isn’t the case here. Which is for things or animals, not people, and that can be used for people in some very formal or restrictive contexts, but who is the clearest and most standard choice when referring to a person who performed the action.