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: Surgery
Renal collar which surrounds the aorta has its two limbs split by - 
Select and explain. 
A. Left renal vein, B. Left renal artery, C. Isthumus of horseshoe kidney, D. All of the above
A: Left renal vein
Answer: A: Left renal vein 
Explanation: • The main renal vein divides and sends one limb anterior and another limb posterior to aorta to reach the IVC.
• Formed on the left side and represents persistence of the embryonic state.