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
The "O" sign in a pure Tone Audiogram indicates - 
Select and explain. 
A. Air conduction of right ear, B. Air conduction of left ear, C. Bone conduction of right ear, D. Bone conduction of left ear
A: Air conduction of right ear
Answer: A: Air conduction of right ear 
Explanation: None