Renal collar which surrounds the aoa has its two limbs split by -

Ans. is 'a' i.e., Left renal vein The left renal vein normally passes anterior to the aoa to join the I.V.C. However sometimes the left renal vein may divide and send one limb anterior and one posterior to the aoa to reach the inferior vena cava k/a venal collar representing persistence of embryological state. Also remember The most common anatomic variant of the renal vessels is --> supernumerary renal aeries.