Answer:
B.) a fact.
Step-by-step explanation:
A.) is incorrect because there is no limit as to how many people can write about a certain topic. If anything, when it comes to opinion/persuasive pieces, the more essays there are, the better. More resources allow the reader to learn about more viewpoints, and thus come to a more informed conclusion.
B.) is correct because the point of a persuasive essay is to try to get the reader to adopt the same opinion as the writer. Facts are non-disputable. A writer may be able to back up their persuasive argument with evidence, but the standpoint itself is not absolute.
C.) is incorrect because there is no reason as to why someone cannot write many essays about a certain viewpoint. Sometimes people write additional essays because there is new evidence, they wish to refute someone else's argument, etc.