1). Montresor carries out his wicked revenge on Fortunato during a carnival. This means that everyone will be out and about enjoying themselves, and so there won't be anyone around to notice Montresor luring Fortunato down to the catacombs. As it's carnival time, Fortunato is also wearing motley, or a jester's costume, which will make it virtually impossible for anyone to identify him, even if they weren't already preoccupied with having a good time.
2). Montresor chooses the carnival as he knows that all his servants will be out enjoying themselves, along with everyone else. It's not enough for Montresor to kill Fortunato; he has to get away with it as well. And what better way to avoid being caught than to ensure that there's absolutely no one around to witness this dastardly crime and its aftermath?
3). Montresor expertly plays upon Fortunato's enormous vanity. Fortunato fancies himself as a wine connoisseur, and Montresor knows that his sworn enemy will be unable to resist the...
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