No, I have never met . . . . . . A. It B. him C. them D. her

The pronoun “them” is used to refer to two or more people or things. In the sentence “No, I have never met them,” the speaker could be saying that they have never met two or more people, or that they have never met a group of people.

The pronoun “her” is used to refer to a female person. In the sentence “No, I have never met her,” the speaker is saying that they have never met a female person.

In this case, the speaker is most likely saying that they have never met a male person.