I believe that it is "C. Minor supporting detail" But I still have some doubts, so it may be "B. Major supporting detail"
Because it merges the fairy tale stories of the past with the cynicism, and wit of the current generation
Explanation:
The book 'The Princess Bride' is one of the best fairy tales and an example of the form being relevant even in a time when it is not.
The author has deftly used the trope of the form to his advantage and written a classic fairy tale with a setup of folk and traditional tales.
At the same time, the book is original enough and relevant enough for the current generation and holds up with updated humor and wit of this generation.
