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': 'In a patient of known prolonged congenital QT syndrome and intermittent Torsade-de-pointes, which of the following should be prescribed? \nSelect and explain. \nA. Magnesium sulphate, B. Metoprolol, C. Cardiac pacing, D. Isoprendine', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Metoprolol", 'role': 'assistant'}]