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: Unknown
[{'content': 'Mc Ewan triangle is formed by all except: \nSelect and explain. \nA. Posterosuperior bony canal wall, B. Temporal line, C. Floor of bony canal wall, D. Tangential line drawn to the EAC', 'role': 'user'}, {'content': 'Answer: C \nExplanation: McEwans triangle is bounded by temporal line, postero-superior canal wall and a tangential line to the external auditory canal. This triangle segment overlies mastoid antrum. This is an important anatomical landmark in mastoid surgery.', 'role': 'assistant'}]