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': 'Which of the following drug is useful in prophylaxis of migraine? \nSelect and explain. \nA. Propranalol, B. Sumatriptan, C. Aspirin, D. Ergotamine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Migraine: Propranolol\xa0is\xa0the\xa0most\xa0effective\xa0drug for\xa0chronic\xa0prophylaxis\xa0or migraine.\u200b\nDrug therapy of migraine', 'role': 'assistant'}]