This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
Symbol 'X' denotes 
Select and explain. 
A. Air conduction threshold for right ear, B. Bone conduction threshold for right ear, C. Air conduction threshold for left ear, D. Bone conduction threshold for left ear
C: Air conduction threshold for left ear
Answer: C: Air conduction threshold for left ear 
Explanation: .An "O" often is used to represent responses for the right ear and an "X" is used to represent responses for the left ear. A key on the audiogram, similar to one found on a map, identifies what the different symbols mean Hence, indicates air conduction test for left year Ref physiology textbook A. K Jain.. 3e