This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
Decreased bone conduction in an audiogram indicates: 
Select and explain. 
A. Tympanic membrane perforation, B. Ossicular dislocation, C. Ossicular fixation, D. Damage to cochlea
D: Damage to cochlea
Answer: D: Damage to cochlea 
Explanation: Bone conduction is a measure of cochlear function. This is tested either by Schwabach test or absolute bone conduction test or audiometrically by placing the vibrator on the mastoid bone. Decreased bone conduction or loss of it indicates hypoactive or non-functioning cochlea. All other conditions listed in (a), (b) and (c) cause conductive hearing loss with cochlear function remaining normal.