large number of satirical plays that were written about him during his administration.- Flavius was widely unpopular among his subjects
AB
A concludes B. B entirely depends on A. It means there can not be other factors C that can also contribute to B. This is flaw in argument.


(A) fails to consider the percentage of plays written during Flavius’s administration that were not explicitly about Flavius
Wrong: Irrelevant as it doesn’t affect our conclusion ; large number of plays is given already

(B) treats the satirical plays as a reliable indicator of Flavius’s popularity despite potential bias on the part of the playwrights
Correct: A is only factor B. That’s how argument concludes. Explained in our analysis

(C) presumes, without providing evidence, that Flavius was unfavorably disposed toward the arts
It is given in argument. We no need to concern about evidence.

(D) takes for granted that Flavius’s attempt to discourage the arts was successful
Wrong : It is independent of effect on conclusion.

(E) fails to consider whether manual labor and moral temperance were widely regarded as virtues in ancient Rome
Wrong: Irrelevant to F popularity

Conclusion: Flavius discouraged the arts, by removing state financial support for them, and was widely unpopular because the large number of satirical plays were written about him.

What if "removing state financial support" somehow spurred art?
What if plethora of satirical plays were written because of admiration or something else?

(B) treats the satirical plays as a reliable indicator of Flavius’s popularity despite potential bias on the part of the playwrights