This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
[{'content': 'Mc Ewans triangle is located on \nSelect and explain. \nA. Mastoid antrum, B. Inner ear, C. Cochlea, D. Saccule', 'role': 'user'}, {'content': "Answer: A \nExplanation: MacEwen's triangle is bounded by temporal line,posterosuperior segment of bony external auditory canal and the line drawn as a tangent to the external canal. It is an impoant landmark to locate the mastoid antrum in mastoid surgery. Reference-Dhingra 6/e,p 6.", 'role': 'assistant'}]