Answer:
B. Symbol.
Step-by-step explanation:
Edgar Allen Poe's short story "The Fall of The House of Usher" is a form of gothic romanticism which deals with the themes of supernatural elements in play. Through the character of the Usher family and the house, including our narrator/ protagonist, the story describes how the House of Usher came to crumble.
Towards the end of the story, the unnamed narrator tells of how he used "The Mad Trist" by Sir Lancelot Canning to calm Roderick Usher. Although this is a poem, the narrator used it as a story to pacify his friend Roderick, who had been greatly agitated. Poe used this 'story' as a way to romanticize the story, but yet symbolic of the deterioration of Madeline Usher's body. But Madeline's body escapes from the iron vault, paralleling her actions with those of the very words or scenes that the narrator is narrating to Roderick while reading the story.