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 tubuloglomerular feedback is me\xaddiated by: \nSelect and explain. \nA. Sensing of Na+  concentration in the macula densa, B. Sensing of HCO3 - concentration in macula densa, C. Sensing NaCl concentration in the macula densa, D. Opening up of voltage gated Na+ channels in afferent arteriole', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Macula densa sense both Na+\xa0and Cl-\xa0, but Cl-\xa0is more important.', 'role': 'assistant'}]