How Does the Fallacy of Appeal to Authority Involve Credibility

How does the fallacy of appeal to authority involve credibility?

A) It assigns expert credibility to someone who doesn't deserve it.
B) It fails to recognize the credibility of someone who is an expert.
C) It assigns too much credibility to an opponent.
D) It attacks the credibility of an opponent, rather than what he or she is saying.
E) It ignores the issue of whether or not an opponent has credibility.