Which of these excerpts from Mark Twain's Life on the Mississippi best shows Twain's subtle sense of humor?
A. At last he turned up as apprentice engineer or "striker" on a steamboat. This thing shook the bottom out of all my Sunday-school teachings.
B. The white town drowsing in the sunshine of a summer's morning; the streets empty, or pretty nearly so; one or two clerks sitting in front of the Water Street stores . . .
C. The captain lifts his hand, a bell rings, the wheels stop; then they turn back, churning the water to foam, and the steamer is at rest.
D. The pilot, even in those days of trivial wages, had a princely salary—from a hundred and fifty to two hundred and fifty dollars a month, and no board to pay.