Your tone
Let's look at the other choices first. Your credibility is your ability to be believed as trustworthy in regards to the subject. Whether you're talking to a group of teenagers or professional adults, your credibility doesn't change. Your clarity also should not change based on the audience because you want to be clear in your message at all times. Also, your purpose should be the same no matter the audience. The only thing that would change is your tone. The way you approach a crowd of teenagers would vary greatly from the way you'd approach a room of professionals.
(D) because "an apprentice" is singular, so it should have singular pronouns. "Their" should be "his or her."
The answer is C. The story never had anything about prison, and the story clearly states that the doctor was there. also the doctor didn't seem to bother the man he only passed by. SO C is your only logical answer
The answer is
A. Onomatopoeia. :)