Question

In which sentence is the pronoun whom correctly used?

She is the woman whom, I think, is an expert on whales.

It was he whom led the whaling expedition.

Whom is hoping to go on the whaling expedition?

From whom did you borrow the book about whales?

Answer 1

From whom did you borrow the book about whales

Answer 2

4. From whom did you borrow the book about whales?

Whom is a pronoun that refers to the object of a verb or preposition, meaning that "whom" does not perform the main action, but, instead, it receives the action. Therefore, when answering questions with "whom", the answer may be expressed with object pronouns, namely, me, us, you, him, her, its, them. Furthermore, "whom" can be found near a preposition such as "to", "from".

" From whom did you borrow the book about whales?" is the correct option because the question is asking about the object of the action, not the subject. If we were to answer the question, we may use an object pronoun. For example, one possible answer: "I borrowed the books about whales from David/him"

"I" is the subject (the one that performs the main action "borrow the books") and "David" ("him") is the object as he receives the action.

All other options are incorrect because, instead of "whom", there should be a "who", since option 3 asks about the subject of the main action, and option 1 and 2 refers to the subject of the sentence.