Final answer:
In 'The Cask of Amontillado,' Montresor describes his family's coat of arms as featuring a serpent being crushed by a human foot.
Step-by-step explanation:
The animal that Montresor claims is depicted on his family's coat of arms in Edgar Allan Poe's short story, 'The Cask of Amontillado,' is a serpent. This is noted during a conversation between Montresor and Fortunato, where Montresor describes his family arms as 'A huge human foot d'or, in a field azure; the foot crushes a serpent rampant whose fangs are imbedded in the heel.' Therefore, the correct answer is A) Serpent.