Formal style, it's pretty easy to figure that out by just canceling out the other answers. Slang is obviously not it, I don't see anything critical in this, and I don't know how it could be informal.
Answer:
tone and viewpoint.
Explanation:
I did it on ed and it was right, sorry for it being to late :)
A single sentence that summarize the whole chapter 27 of the absolute true diary of a part time Indian
The answer is C. I think.
