This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
Torus aoicus is an impression in the cavity of 
Select and explain. 
A. Right atrium, B. Right ventricle, C. Left ventricle, D. Left atrium
A: Right atrium
Answer: A: Right atrium 
Explanation: Torus aoicus (aoic mound) is the prominent region of the right atrial septum, which marks the projection of the non-coronary aoic sinus into the right atrial wall. The bulge is superior to the coronary sinus and anterior to the fossa ovalis.