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
[{'content': 'The primary active step for sodium reabsorption in the proximal tubule involves: \nSelect and explain. \nA. Sodium-glucose cotranspo across the luminal membrane, B. Sodium/hydrogen ion counteranspo across the luminal membrane, C. Sodium transpo the Na+-K+-ATPase at the basolateral membrane, D. Sodium-amino acid cotranspo across the luminal membrane', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Sodium transpo the Na-K-ATPase at the basolateral membrane. This is the only transpo step for sodium in the proximal tubule that involves the direct input of energy to move sodium against its electrochemical gradient (in this case from the inside of the cell to the outside).', 'role': 'assistant'}]