Read these sentences from "the cask of amontillado." "enough," he said; "the cough is a mere nothing; it will not kill me. i shall not die of a cough." "true—true," i replied. which literary technique is employed in these sentences?

The right answer is foreshadowing.

Explanation: Just to elaborate a little on the answer, it can be added that by hinting at what may happen in the future—Fortunato will eventually die, and indeed not of a cough, but by being buried alive—Poe is employing foreshadowing. Fortunato says that his cough will not kill him, to what Montresor replies "true—true," since he well knows that that's not going to be the cause of his death. An humiliated and vindictive Montresor will bury him alive. This technique keeps the reader engaged and interested.    

being ignored by someone and then accepting the fact was really tough