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: Medicine
[{'content': 'Which differentiating prerenal azotemia with ATN features favoring pre-renal azotemia -a) Urine osmolality > 500 mosmol/kgb) Sodium spot excretion < 10 ml/Lc) Fractional excretion of sodium > 1d) Plasma BUN/creatinine ratio < 20 \nSelect and explain. \nA. ac, B. a, C. ab, D. bc', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]