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': 'Carharts notch in audiogram is deepest frequency of - \nSelect and explain. \nA. 0.5 KHz, B. 2 KHz, C. 4 KHz, D. 8 KHz', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]