Why is it important to the plot that the American is a "naturalist"?

a
Because he studies nature, he's unaware of why the snake would go toward the bowl of milk.
b
Because he studies nature, he's aware of the snake long before Mrs. Wynnes is and uses his knowledge to keep the guests busy.
c
Because he studies nature, he's first to see why the discussion about men versus women is correct.
d
Because he studies nature, he's quick to recognize why Mrs. Wynnes stiffened up and called for the house boy to put out the bowl of milk.