What evidence leads you to believe that the tone of the passage is academic?

The narrator mixs up his words and sounds confused.

Typically when the narrator uses information that you could probably find somewhere trustworthy, like a textbook and goes on to give specific information that you would need to know for a unit or group of tests. For example, if the passage says "Christopher Columbus didn't actually mean to find the Americas, I guess you could say it was a happy mistake." That would be academic.