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
Therapeutic level of phenytoin is: 
Select and explain. 
A. 0-9 mu g/ml, B. 10-19 mu g/ml, C. 20-29 mu g/ml, D. 30-39 mu g/ml
B: 10-19 mu g/ml
Answer: B: 10-19 mu g/ml 
Explanation: Ref: Katzung 11/e p404 The therapeutic level of phenytoin is 10-20 micro g/ml.