In an essay written in a formal style, the kind of tone that the writing should have is: Objective.
An objective tone is a tone where the writer states the facts of a matter. He takes no sides but simply states matters as they are. When writing a formal essay, it important to be objective.
This will require that the facts of the matter are presented and backed by evidence. So, option C is right.
Learn more about formal essays here:
brainly.com/question/3269510
First Question: http://www.sparknotes.com/lit/uncletom/themes.html
Second Question: http://www.sparknotes.com/lit/uncletom/themes.html
