Answer:
an is use for nouns that start with vowels while a is for nouns that start with non vowels
If Joey decided to take Pre-Calculus his senior year in high school because he plans to go to college then this is a wise decision that puts future goals ahead of short-term fun.
I would choose letter C because plots are used in writing a story, but nonfiction papers are more informational and focus on a specific topic. They do not go through events like stories do.