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: Unknown
[{'content': 'What is the clearance of a substance when its concentration in the plasma is 10 mg/dl, its concentration in the urine is 100 mg/dl & urine flow is 2 ml/min: \nSelect and explain. \nA. 2 ml/min, B. 10 ml/min, C. 20 ml/min, D. 200 ml/min', 'role': 'user'}, {'content': "Answer: C \nExplanation: The Clearance of a Substance 'X' is equal to the concentration of substance X in urine (UX) times the urine flow per unit of time (V.) divided by the arterial plasma level of X (PX), or UXV./PX.\nThis value is called the clearance of X (CX).", 'role': 'assistant'}]