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': "Gelle's phenomenon is absent in - \nSelect and explain. \nA. CSOM, B. Tympanosclerosis, C. Meniere's disease, D. Otosclerosis", 'role': 'user'}, {'content': "Answer: D \nExplanation: Gelle's test compares intensity of bone conducted tuning fork sound without and with raising pressure on the tympanic membrane with Siegel's speculum.Normally,Gelle's test is positive because intensity of hearing decreases when air pressure is raised in external auditory canal.In ossicular fixation or ossicular discontinuity,increased air pressure makes no changes in the sound intensity(Gelle's negative) REF.Diseases of EAR,NOSE and THROAT Ref:PL Dhingra 6th Edition page no.447", 'role': 'assistant'}]