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
[{'content': 'The principal site of acidification of urine is \nSelect and explain. \nA. Loop of henle, B. Collecting duct, C. DCT, D. PCT', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The cells of the proximal and distal tubules secrete hydrogen ions. Acidification also occurs in the collecting ducts. The reaction that is primarily responsible for H+ secretion in the proximal tubules is Na+-H+ exchange. Na is absorbed from the lumen of the tubule and H is excreted. Ref: guyton and hall textbook of medical physiology 12 edition page number:504,505,506', 'role': 'assistant'}]