This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
[{'content': 'Cholesteatoma commonly perforates: \nSelect and explain. \nA. Lat. Semicircular canal, B. Sup. semicircular canal, C. Promontory, D. Oval window', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is a i.e. Lateral semicircular canal Cholesteatoma has the propey to destroy the bone by viue of the various enzymes released by it. Structures immediately at the risk of erosion are: - Long process of incus.deg - Fallopian canal containing facial nerve.deg - Horizontal/lateral semicircular canal.deg', 'role': 'assistant'}]