Which excerpt from "the cask of amontillado" best infers what will be fortunato's downfall?

a) the gait of my friend was unsteady, and the bells upon his cap jingled as he strode
b) he had a weak point --this fortunato --although in other regards he was a man to be respected and even feared. he prided himself on his connoisseurship in wine.
c) "nitre," i replied. "how long have you had that cough? "
d) "my friend, no; i will not impose upon your good nature. i perceive you have an engagement. luchresi--"