Answer: C. Mr. Moon, whom you have met , is my assistant.
A relative pronoun is a kind of pronoun that is used to attach a phrase to a noun or a pronoun. In the sentence above, the relative pronoun is "whom". Other examples of relative pronouns include that, whichever, who, and which. Below are some examples of sentences that contain relative pronouns.
I have one true love, the one that got away.
She is my mother, the one who gave me everything.
She chose the lavender dress which is more revealing.