Answer: B. Humorous
Explanation: The tone of the opening passages meant to be humorous and to engage the reader into reading on into the story.
The tone is how the writer feels, remember that.
Dissatisfied means the writer wasn't not content or happy with something, which is not true in this case.
It's obviously not unhappy because that is the same thing as dissatisfied.
Sarcasm is language that is strongly negative and often shows anger about something or mocks an opposing point of view. The writer was not being sarcastic while writing this opening passage.
The writer had a rather humorous tone. Remember that in the "The Gift of the Magi" by O. Henry, the tone is rueful and affectionate. Rueful is expressing sorrow or regret, especially when in a slightly humorous way. This confirms the tone was humorous.