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': 'On otological examination all of the following with have positive fistula test except - \nSelect and explain. \nA. Dead ear, B. Labyrinthine fistula, C. Hypermobile stapes footplate, D. Following fenestration surgery', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]