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
Threshold of hearing in a young normal adult is ? 
Select and explain. 
A. 0 dB, B. 10 dB, C. 20 dB, D. 30 dB
A: 0 dB
Answer: A: 0 dB 
Explanation: Ans. is'a'i.e.,0 dBAudiometric zeroThreshold of hearing, i.e. The faintest intensity which a normal healthy person can hear will vary from person to person.The International Standards Organisation (ISO) adopted a standard for this, which is represented as the zero level on the audiometer (0 dB).According to ISO, audiometric zero is the mean value of minimal audible intensity in a group of normally hearing healthy young adults.