Answer: A) The writer could make the tone more academic.
Explanation: The tone of a text or sentence is the author's or speaker's attitude towards the audience, the subject or even the characters of the text. There are many different kinds of tones, like: positive, negative, objective, sad, angry, etc. From the given options, the one that represents how the excerpt could be best improved, is the corresponding to option A: A. The writer could make the tone more academic, by avoiding expressions like "totally important," "tons," and "it's obvious."
For 17 number 4. For 18 number 1. For 20 number 4. Hope this helped.