Final answer:
An index is not an element of a genre. Elements of a genre include style, plot, and theme, essential for categorizing various forms of literature. Index is a structural element found in books, not related to genre classification.
Step-by-step explanation:
The elements of a genre include style, plot, and theme. These components are essential in categorizing literature into different genres, such as creative nonfiction, fiction, drama, and poetry, as well as their respective subgenres like short stories, flash fiction, lyric poetry, etc. Genres can also encompass the narrative form used in literature, for instance, an epistolary form with a series of letters, or a mix, like in Frankenstein with a journal within a letter.
Furthermore, a genre typically does not include an index. An index is a list found at the end of a book, listing the names, subjects, etc. that are mentioned in the text, along with the pages on which they are mentioned, which is a structural element rather than a genre characteristic. Therefore, the element that is not part of a genre from the options provided is D) Index.