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': 'Impedance audiometry is done using frequency probe of- \nSelect and explain. \nA. 220 Hz, B. 555 Hz, C. 440Hz, D. 1000 Hz', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]