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': 'Longest acting nitroglycerin is: \nSelect and explain. \nA. Amyl nitrite., B. Penta erythrital tetranitrate., C. Isosorbide dinitrate, D. Isosorbide mononitrate.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]