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': 'Investigation in a patient of oliguria revealed Urine osmolity 620 mosm/kg Urine sodium :12mmol/L Urine /plasma urea ratio :13 :1 The most likely diagnosis is - \nSelect and explain. \nA. Prerenal acute renal failure, B. Acute tubular recrosis, C. Acute cortical necrosis, D. Urinary tract obstruction', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]