What example of irony can be seen in the following passage
of "The Invalid's Story"?

Section 5- setting things to
rights, and all the time
contentedly humming "Sweet
By and By" in a low tone, and
flatting a good deal.

A. He was humming "Sweet By and By"
but it smelled the opposite of sweet.
B. He was humming quietly, but the
narrator was yelling loudly.
C. It was quiet in the front car of the train
and loud in the back car of the train.