Final answer:
The difference between a novel and a novella is the length, with a novel being longer than a novella. Both can have multiple sub-plots and follow different narrative structures.
Step-by-step explanation:
The main difference between a novel and a novella lies in their length; A) a novel is longer than a novella. Novels tend to delve into more complex plots, have a larger cast of characters, and span over a longer period of time. On the other hand, novellas are shorter than novels but longer than short stories, offering a concise but detailed storytelling experience. It's a common misconception to think that a novel has no sub-plot or that a novella doesn't follow an established narrative structure like Freytag’s Pyramid. In truth, both novels and novellas can have multiple sub-plots and can either adhere to or diverge from traditional narrative structures.