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
According to WHO classification, for severe degree of impairment of hearing is at - 
Select and explain. 
A. 26 - 40 dB, B. 41-55 dB, C. 56-70 dB, D. 71-91 dB
D: 71-91 dB
Answer: D: 71-91 dB 
Explanation: None