Final answer:
Fortunato's fondness for wine leads to his downfall in Edgar Allan Poe's 'The Cask of Amontillado', as it allows Montresor to manipulate him into the catacombs, where Montresor enacts his revenge.
Step-by-step explanation:
In The Cask of Amontillado by Edgar Allan Poe, Fortunato's downfall is brought about by his fondness for wine. This is highlighted when the narrator, Montresor, who seeks vengeance, lures Fortunato into the catacombs with the promise of tasting a rare vintage of Amontillado. Fortunato, who prides himself on his connoisseurship in wine, is unable to resist the temptation. This foreshadows the dark turn the story takes as Montresor uses Fortunato's eagerness against him to fulfill his own plot for revenge.
The correct answer to the question is thus: A) Wine. Fortunato's expertise and pride in his knowledge of wine make him an easy target for Montresor, who exploits Fortunato's desire to showcase his skill in discerning fine wines. This detail is crucial to the unfolding of the plot and ultimately leads to Fortunato's tragic end.