This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
in the aboove show triangle posteror border is formed by ? 
Select and explain. 
A. bony labrynth, B. sigmoid sinus, C. superior petrosal sinus, D. CAVERNOUS SINUS
B: sigmoid sinus
Answer: B: sigmoid sinus 
Explanation: THIS IS THE IMAGE OF TRAUGHTMANNS TRIAGNLE REF : GRAYS ANATOMY