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': 'Simple mastoidectomy is done in -a) Acute mastoiditisb) Cholesteatomac) Coalescent mastoiditisd) Localized chronic otitis media \nSelect and explain. \nA. a, B. bc, C. ac, D. b', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Simple mastoidectomy is used in acute coalescent mastoiditis.', 'role': 'assistant'}]