This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Otosclerosis, Subject name: ENT
Carhart's notch dips at: 
Select and explain. 
A. 2 Hz, B. 200 Hz, C. 2000 Hz, D. 2000 MHz
C: 2000 Hz
Answer: C: 2000 Hz 
Explanation: Ans. (c) 2000 Hz* Carhart Notch is an audiogram finding and is an important feature in patients with Otosclerosis.* There is a sudden dip (notch) at 2000 Hz in bone conduction curve.* Carhart s notch disappears after stapedectomy.