This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
[{'content': 'Headache is commonly seen with which anti-anginal drug? \nSelect and explain. \nA. Beta blockers, B. Nitrates, C. Trimetazidine, D. Potassium channel openers', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Nitrates produce headache because of vasodilatation of meningeal vessels. Ref katzung 12th ed.', 'role': 'assistant'}]