Final answer:
The best example of ethos from the sentences provided is Option D, as it demonstrates the writer's hard work and experience, which elicit respect and trust from the reader, central components of ethos.
Step-by-step explanation:
When identifying the best example of ethos in the given sentences from a letter, it is important to understand that ethos is an appeal to the writer's credibility or character. Ethos convinces the audience of the author's credibility or trustworthiness.
Option D, "I had to bleed and I had to sweat just as hard as any other elite athlete," is the strongest example of ethos. This sentence demonstrates the writer's hard work and determination, qualities that tend to elicit respect and trust from the reader, which are central to ethos.
The author's experience and sacrifice imply a level of commitment and authority on the topic of being an athlete, which serves to bolster their credibility. While the other options may establish a connection with the reader or provide a background story, they do not directly establish the writer's credibility in the same manner as Option D does.