This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Embryology, Subject name: Anatomy
First organ to attain functional maturity is: 
Select and explain. 
A. CVS, B. CNS, C. GIT, D. Lungs
A: CVS
Answer: A: CVS 
Explanation: Ans. A CVSRef: Netter's Clinical Anatomy, 3rd ed. pg. 35* CVS is the first fully functional organ system in fetus and first to attain maturity from functional perspective.