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
Carha's notch in an audiogram represent which of the following deepest frequency? 
Select and explain. 
A. 0.5 KHz, B. 2 KHz, C. 4 KHz, D. 8 KHz
B: 2 KHz
Answer: B: 2 KHz 
Explanation: Carha's notch is seen in patients with otosclerosis. It is a dip in the bone conduction curve seen maximally at 2 KHz region. It disappears after successful stapedectomy.