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
The most impoant structure involved in development of inferior vena cava is ? 
Select and explain. 
A. Supracardinal vein & Subcardinal vein, B. Umbilical vein, C. Anterior cardinal vein, D. Posterior cardinal vein
A: Supracardinal vein & Subcardinal vein
Answer: A: Supracardinal vein & Subcardinal vein 
Explanation: A i.e. Supracardinalvein & subcardinal vein