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: Unknown
[{'content': 'This tumour arises from: \nSelect and explain. \nA. Epitympanum, B. Hypotympanum, C. Mesotympanum, D. Inner ear', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]