The story is told from Montresor’s point of view – thus we know all that he is thinking.  Indeed, he has told us at the beginning of the story that he is seeking to exact revenge on Fortunato for “the thousand injuries” inflicted upon Montresor by the man.  He also states “that neither by word or deed had I given Fortunato cause to doubt my good will.”  Fortunato, therefore, believes Montresor still to be a friend.  Given this information, had the story been told from the point of view of Fortunato, we might assume that Montresor was indeed concerned about his health.  However, given what Montresor has already told us, we know that this is the least of his concerns.  Indeed, if answer (A) were true, there would be no element of sarcasm at all.  We also know that he is only mentioning Luchresi’s name to sustain Fortunato’s interest in the amontillado – Luchresi being, as Fortunato states, “an ignoramus” who “cannot tell Amontillado from Sherry.”  And, being as there is in fact no existing cask of amontillado, Montresor has no intention of going to Luchresi, and so we can eliminate (B).  Nowhere in the story or in the passage does it mention any sort of jealousy on Montresor’s part for Fortunato’s wealth, so we can also eliminate response (D).

Given all this information, we can conclude that the correct answer is (C), that Montresor is unconcerned for Fortunato’s health.  We know from the very beginning that Montresor will kill Fortunato, or injure him in some other way, and so the man’s health is of absolutely no concern to him.  But by stressing the opposite, and mentioning Luchresi, he is playing with Fortunato’s pride, and therefore convinces him to walk unsuspectingly into the deepest, darkest reaches of his cellar.