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': "A 30 years woman presents with progressive conductive deafness bilaterally. The most common cause is - \nSelect and explain. \nA. Tympanosclerosis, B. Otospongiosis, C. Meniere's disease, D. Bilateral wax in external ears", 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]