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
Triangle of koch is made by: 
Select and explain. 
A. Posterior leaf-let of mitral valve, B. Coronary sinus opening, C. Superior vena cava opening, D. All
B: Coronary sinus opening
Answer: B: Coronary sinus opening 
Explanation: B i.e. Coronary sinus opening