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
Mc Ewan triangle is formed by all except: 
Select and explain. 
A. Posterosuperior bony canal wall, B. Temporal line, C. Floor of bony canal wall, D. Tangential line drawn to the EAC
C: Floor of bony canal wall
Answer: C: Floor of bony canal wall 
Explanation: 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.