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
Base of the hea is formed by ? 
Select and explain. 
A. Right atrium, B. Right ventricle, C. Left atrium, D. Left ventricle
C: Left atrium
Answer: C: Left atrium 
Explanation: Ans. is `c > a' i.e., Left atrium > Right atrium