Concept:A narrative composed in the form of a letter is known as an epistolary novel.Explanation:The term "epistolary" is derived from "epistle," which means a letter.In an epistolary novel, the story is told through letters, diary entries, or other personal documents.This narrative style allows readers to see events through the direct thoughts and correspondence of the characters.Well-known examples include Samuel Richardson's Pamela and Bram Stoker's Dracula.Answer:Option B. an epistolary novel.