This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidneys and Body Fluids, Subject name: Physiology
[{'content': 'The prime driving force for counter current multiplier system is \nSelect and explain. \nA. Medullary hyperosmolarity, B. Reabsorption of Na+ in thick ascending limb, C. Action of ADH via aquaporin channels, D. Urea recycling', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Reabsorption of Na+ in thick ascending limb(Ref: Ganongy 25th ed/p.685)The primary driving force for counter current system is Reabsorption of Na+ in thick ascending limb through Na-K-2Cl cotransporter', 'role': 'assistant'}]