<prompt> The prime driving force for counter current multiplier system isMedullary hyperosmolarityReabsorption of Na in thick ascending limbAction of ADH via aquaporin channelsUrea recycling  <response>: Ans. b Reabsorption of Na in thick ascending limbRef: Ganongy 25th edp.685The primary driving force for counter current system is Reabsorption of Na in thick ascending limb through Na-K-2Cl cotransporter 