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.