Answer:
Purpose
Step-by-step explanation:
To talk about the purpose of a piece of nonfiction is equal to talking to the intentions or the reasons why the author wrote that piece of writing. To determine the purpose of a story is essential to fully grasp the meaning of the story.
The other options are incorrect because style refers to the manner in which the writer expresses; tone is the way the author approaches the subject of a story and it is created through word choice, syntax and the level of formality; and perspective is also incorrect because it refers to the point of view from which the story is told, whether first, second or third person.