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 seen at: 
Select and explain. 
A. 0.5 KHz, B. 1 KHz, C. 2 KHz, D. 4 KHz
C: 2 KHz
Answer: C: 2 KHz 
Explanation: Ans: c (2 KHz) Ref: Dhingra, 3rd ed, p. 115 & p. 87Dip in bone conduction in otosclerosis & maximum occurs at 2000 Hz called Carhart notchDip Disappears after successful stapedectomy2 KHz dip - Otosclerosis4 KHz dip - Noise induced hearing loss8 KHz dip - Senile otosclerosis