The correct answer is A. Ms Jones, whom you have met, is my teacher.
Step-by-step explanation
A relative pronoun is a word that is used to refer to a noun (a person or a thing) mentioned previously and for which you want to add more information. Relative pronouns can refer to singular or plural objects. Some relative pronouns can be used only with people, others only with things, and some with both. Within the Relative Pronouns.
Relative pronouns are: "that" and "whose" that can be used with people and objects; "which" that is used only with objects; and "who" and "whom" are used only with people. According to the above, the sentence that contains a relative pronoun is A. ms. jones, whom you have met, is my teacher.