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': 'True about cholesteatoma -a) Benign tumourb) Bone erosion presentc) MC cause of conductive deafnessd) Found in apex of petrous bone commonlye) Contains cholesterol \nSelect and explain. \nA. c, B. bd, C. ab, D. ac', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]