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: Pharmacology
[{'content': 'What is the clearance of a substance, if its concentration in plasma is 10 mg%, concentration in urine is 100 mg % and urine flow is 2 ml/min ? \nSelect and explain. \nA. 0.02 ml/min., B. 0.2 ml/min, C. 2 ml/min, D. 20 ml/min.', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., 20 ml/min.", 'role': 'assistant'}]