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': 'In tubular necrosis, ratio of urine to plasma creatinine is: \nSelect and explain. \nA. 20, B. 40, C. 20-30, D. 30-40', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Answer is A (20)', 'role': 'assistant'}]