The answer is B. "He asked himself where it had come from and how; the past provided no explanation, and the future could not justify it."
This option is not a dark humor because it does not show the opposite side of happiness. The other choices explain that although there is happiness, he considered it as a burden- making it a dark humor.
I would say the third one
Adverbs contain words like "you"
The chief of police of Beijing gives an opinion that might direct us toward the theme.
