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
[{'content': 'A pure tone audiogram with a dip at 2000Hz is characteristic of \nSelect and explain. \nA. Presbycusis, B. Ototoxicity, C. Otosclerosis, D. Noise induced hearing loss', 'role': 'user'}, {'content': "Answer: C \nExplanation: In otosclerosis, there is a dip in bone conduction curve. It is different at different frequencies but maximum at 2000Hz and is called Carha's notch. Ref: Diseases of EAR, NOSE and THROAT by PL Dhingra; 7th Edition; Page no.96", 'role': 'assistant'}]