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
This drug is a classical example of pharmacological success but therapeutic failure. Reason for its therapeutic failure is coronary steal phenomenon. It is: 
Select and explain. 
A. Glyceryl trinitrate, B. Dipyridamole, C. Propranolol, D. Diltiazem
B: Dipyridamole
Answer: B: Dipyridamole 
Explanation: None