In this, I will be doing the process of elimination.
Option A: This doesn't really make sense because the author has not used any words that would make the reader seem it is sad, so I suppose this one is incorrect.
Option B: This does make sense, however we must read each choice.
Option C: The author doesn't sound upbeat, so this one is incorrect.
Option D: The author does sound quite humorous, so this one makes a little bit of sense.
Now, let's look at the choices that could be correct:
B. Sarcastic
D. Humorous
In conclusion, I believe that the answer should be D. Humorous. However, this is your work so if you believe it is B. Sarcastic, then choose that.