This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Renal physiology, Subject name: Physiology
The function of P cells of the kidney is 
Select and explain. 
A. H+ secretion, B. K+ reabsorption, C. Na+ reabsorption, D. Cl- secretion
C: Na+ reabsorption
Answer: C: Na+ reabsorption 
Explanation: The principal cells reabsorb sodium and water from the lumen and secrete potassium ions into the lumen.