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': 'Ear infection causes throat infection through - \nSelect and explain. \nA. Blood spread, B. Eustachian tube, C. Nasocranial spread, D. Simultaneous infection', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]