Which statement about the words "who" and "whom" is most accurate?

A. "Whom" is an object pronoun.

C. The pronoun "whom" can't be used as the object of a preposition.

D. "Who" can be used as both a subject and object pronoun.

A. "Whom" is an object pronoun is actually the only one that is correct. This is because for B. whom could be an object of a preposition if it was in a sentence with "to whom". For C., who is only a subject pronoun. If it were an object pronoun, a sentence would be like this: "To who does the present go to?".