Final answer:
The narrator is reminded of a "sad little salted slug" by Marcus.
Step-by-step explanation:
The correct answer is A. Marcus. In the story, the narrator sees Marcus crying and compares him to a "sad little salted slug." This comparison highlights Marcus's sadness and vulnerability. The other options, such as a walking duck, a pair of socks, or the neighbor, do not have any connection to the narrator's description of the slug.
Learn more about Comparisons and imagery in literature