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: Anatomy
Suprameatal triangle externally represents: 
Select and explain. 
A. Transverse sinus, B. Promontory of middle car, C. Internal acoustic meatus, D. Mastoid antrum
D: Mastoid antrum
Answer: D: Mastoid antrum 
Explanation: Suprameatal triangle, also known as MacEwen's triangle, is seen in temporal bone of skull, in  norma lateralis view.
It is a small area/depression present posterior and superior to external acoustic meatus.
It forms the lateral wall of mastoid antrum.
It is of importance to surgeons performing cortical mastoidectomy.

Boundaries of Suprameatal triangle:

Superiorly: By supramastoid crest.
Anteriorly: By posterosuperior margin of EAM (external acoustic meatus).
Posteriorly: Vertical tangent to posterior margin of EAM (external acoustic meatus).  
Anteroinferiorly: By presence of suprameatal spine.

Key Concept: 
Suprameatal triangle, also known as MacEwen's triangle, is seen in temporal bone of skull, in norma lateralis view. It represents mastoid antrum.