The correct answer is:
I. Details in the story
II. Historical context.
Explanation:
An author's purpose is the main reason why an author decided to write, it is the main objective of the author and it can be to inform, entertain, persuade or to explain. The purpose of an author can be found by details in the story such as information and facts or in a historical context that helps understand, explain and inform the reader about a specific topic.