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
Voice induced impairment of hearing at - 
Select and explain. 
A. 1000Hz, B. 2000 Hz, C. 3000Hz, D. 4000 Hz
D: 4000 Hz
Answer: D: 4000 Hz 
Explanation: None