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': 'This drug is a classical example of pharmacological success but therapeutic failure. Reason for its therapeutic failure is coronary steal phenomenon. It is: \nSelect and explain. \nA. Glyceryl trinitrate, B. Dipyridamole, C. Propranolol, D. Diltiazem', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]