This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Renal Tubular Reabsorption and Secretion, Subject name: Physiology
[{'content': 'In proximal convoluted tubule H+ is exchanged for? \nSelect and explain. \nA. HCO3, B. K+, C. C1, D. Na+', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) Na+Ref: Guyton physiology 11th ed. / 55* Sodium-hydrogen counter-transport occurs in several tissues.* An important example is in the proximal tubules of the kidneys, where sodium ions move from the lumen of the tubule to the interior of the tubular cell, while hydrogen ions are counter transported into the tubule lumen.', 'role': 'assistant'}]