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': 'Prerenal and renal azotemia is differentiated on the basis of: \nSelect and explain. \nA. Creatinine clearance, B. Serum creatinine level, C. Sodium fraction excretion, D. Urine bicarbonate level', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Answer is C (Sodium Fraction Excretion):', 'role': 'assistant'}]