When an author introduces the characters and the conflict, this is known as the exposition, Option D.
The exposition is the part of a story in which important background information is introduced to the audience; for instance, information about the setting, events occurring before the main plot, characters' back stories, ans the like. Exposition can be transpited through dialogues, flashbacks, characters' thoughts, background details, in-universe media, or the narrator telling a back-story.
