It seems that the important choices for this question are missing, but
anyway, I still managed to find the answer. The sentence in the passage
that Edgar Allan Poe used to foreshadow Fortunato's eventual fate in
this short story "The Cask of Amontillado" is this, "A huge human
foot d'or, in a field azure; the foot crushes a serpent rampant whose
fangs are imbedded in the heel." When a foreshadow is used, this serves
as a hint of what is going to happen next in the flow of the story.