Answer:
C. a problem or struggle in a story
Step-by-step explanation:
The main driver of a story is the conflict at the center of the plot. All of the five plot elements: exposition, rising action, climax, falling action, and resolution stem from the conflict. By definition, conflict is the struggle between opposing forces. The characters in the story act to overcome these forces, and that is how a story is born. In other words, if there is no conflict, there is no story.
Conflict also serves to create tension and other emotions that will engage a reader and draw him in.