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
Which one of the following drugs has narrow therapeutic range ? 
Select and explain. 
A. Propranolol, B. Phenytoin, C. Piroxicam, D. Prazosin
B: Phenytoin
Answer: B: Phenytoin 
Explanation: None