Answer: D. The better one knows a person, the more one discovers his or her faults.
Step-by-step explanation: in the given excerpt we can see the description of how the speaker became disappointed of his/her neighbour after talking to him a couple of times. The narrator had the first impression that the man was interesting but that impression faded over time, so the theme that this excerpt best conveys is that the better one knows a person, the more one discovers his or her faults.