This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax, Subject name: Anatomy
Boundaries of Koch's triangle is not formed by: 
Select and explain. 
A. Tricuspid Valve Ring, B. Coronary Sinus, C. Limbus fossa ovalis, D. Tendon of Todaro
C: Limbus fossa ovalis
Answer: C: Limbus fossa ovalis 
Explanation: Ans. C. Limbus fossa ovalisKoch's triangle, named after the German pathologist and cardiologist Walter Karl Koch, is an anatomical area located in the superficial paraseptal endocardium of the right atrium, which its boundaries are the coronary sinus orifice, tendon of Todaro, and septal leaflet of the right atrioventricular valve. It is anatomically significant because the atrioventricular node is located at the apex of the triangle.