Answer:
I would say that the statement that best shows the author's use of ethos is D: He is not culturally "disadvantaged", but he is culturally "different".
Explanation:
By saying this, the author makes clear for the audience that the person that sustains that there are thirteen months in a year is not very reliable because he is culturally "different"; he has been taught that by traditional people. So, by making that clarification, the author expresses this person's credibility and that is what ethos does: it tries to convince an audience by appealing to the character's credibility (or lack of).
