This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
[{'content': 'Therapeutic level of phenytoin is: \nSelect and explain. \nA. 0-9 mu g/ml, B. 10-19 mu g/ml, C. 20-29 mu g/ml, D. 30-39 mu g/ml', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref: Katzung 11/e p404 The therapeutic level of phenytoin is 10-20 micro g/ml.', 'role': 'assistant'}]