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
[{'content': 'Female with stapedectomy done, has conductive hearing loss at 60 dB. Diagnosis ? \nSelect and explain. \nA. Implant failure, B. Fistula, C. Closure of oval window, D. Tympanic membrane perforation', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Closure of oval window", 'role': 'assistant'}]