Ethos is an appeal to
a. the audience's sense of right and wrong
b. the speaker's credibility
c. the audience's sense of logic
d. the audience's emotions

B. the speaker's credibility

Ethos (Credibility), or ethical appeal, means convincing by the character of the author. We tend to believe people whom we respect. One of the central problems of argumentation is to project an impression to the reader that you are someone worth listening to, in other words making yourself as author into an authority on the subject of the paper, as well as someone who is likable and worthy of respect.

The details that best show evidence of tribal traditions are, "never in the history of his people had a man married a woman who spoke a different tongue” and "it has never been heard," was the verdict of an old man speaking a few weeks later.