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: Physiology
The Principal site of absorption of Sodium is : 
Select and explain. 
A. Proximal convoluted tubule, B. Distal convoluted tubule, C. Loop of Henle (thick poion), D. Collecting duct
A: Proximal convoluted tubule
Answer: A: Proximal convoluted tubule 
Explanation: A i.e. Proximal convoluted tubuleNormally about 60% of the filtered Na+ is reabsorbed in the proximal tubuleQ.Sodium ReabsorptionPercentageSite60%Proximal tubuleQ (by N a+ - H+ exchange)30%Thick ascending limb (by Na+ - 2C1+ - K+ cotranspo)7%Distal convoluted tubule (by Na+ - Cl- cotranspo)3%Collecting duct. ( ENaC channels)