This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excretory System (Kidney, Bladder) Acid-Base Balance, Subject name: Physiology
[{'content': 'The region of a nephron where P cells (principal cells) are located is: \nSelect and explain. \nA. PCT, B. Loop of Henle, C. DCT, D. Collecting duct', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Collecting ducts have 2 cell populations: P cell / principle cell: Reabsorb Na+Secrete K+ Intercalated cell: Absorb K+Secrete H+, HCO3- it is the buffering cell in the kidney.', 'role': 'assistant'}]