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: ENT
[{'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: Cholesteatoma has the property to destroy the bone by virtue of the various enzymes released by it.\nStructures immediately at the risk of erosion are:\n\n– Long process of incus.Q\n– Fallopian canal containing facial nerve. Q\n– Horizontal/lateral semicircular canal. Q', 'role': 'assistant'}]