The correct answer is C. Humor
Step-by-step explanation:
A short story is a type of narrative short text that usually tells a fiction set of events, because of this short stories must always include characters (individuals involve in the events), a plot (development of events), setting (context where events occur), theme (main message or idea) and conflict (situation character faces). However, "humor" is not one of the elements that are essential in a short story, instead, this is included depending on the author and for many readers, it makes the short story more interesting but a story is complete without it.