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: Unknown
[{'content': 'Magnesium sulphate potentiates the hypotensive action of - \nSelect and explain. \nA. Methyldopa, B. Nifedipine, C. Enalapril, D. Hydralazine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ans-B', 'role': 'assistant'}]