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': 'Nasopharyngeal Ca causes deafness by: \nSelect and explain. \nA. Temporal bone metastasis, B. Middle ear infiltration, C. Serous effusion, D. Radiation therapy', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Nasopharyngeal carcinoma spreads to Eustachian tube, blocks it and causes Serous Otitis Media which in turn causes Conductive hearing loss.', 'role': 'assistant'}]