Answer:
A. A reference to the author's 15 years as a district court judge
Step-by-step explanation:
Ethos is a mode of persuasion that uses or mentions a source or figure that shows credibility, expertise, prestige or character in order to convince an audience on something. Therefore, when a speaker or writer makes a reference to an author's 15 years as a district court judge, he or she is using a figure whose opinions should be considered valid and credible due to the author's expertise, in other words, it is using ethos.