This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
[{'content': 'Which differentiating prerenal azotemia with ATN features oring pre-renal azotemia - \nSelect and explain. \nA. Urine osmolality > 500 mosmol/kg, B. Sodium spot excretion < 10 ml/L, C. Plasma transferrin/Ig ratio, D. All the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The normal kidney can elaborate urine with a maximum concentration greater than 1,200 mOsm/kg in states of dehydration. A urinary osmolality (Uosm) greater than 500 mOsm/kg,, is highly suggestive of prerenal azotemia Ref Harrison20th edition pg ,299', 'role': 'assistant'}]