Answer:
A. help the reader visualize the setting of the Young's shabby apartment.
The concrete details in the passage, such as the letterbox into which no letter would go and the non-functional electric button, help paint a vivid picture of the shabby condition of the vestibule in the Youngs' apartment building. The description of the card bearing the name "Mr. James Dillingham Young" further adds to the visual imagery of the setting. It suggests that the apartment building is not well-maintained and may be in a state of disrepair, setting the tone for the overall condition of the Youngs' living situation.