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': 'Which of the following is a venodilator? \nSelect and explain. \nA. Hydralazine, B. Minoxidil, C. Nitroprusside, D. Nifedipine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Nifedipine is a calcium channel blocker- aeriolar dilator Minoxidil is potassium channel opener - aeriolar dilater. Hydralazine is also an aeriodilater. Nitrates are preferably venous dilators (REF.Essential of medical pharmacology KD TRIPATHI 8th Edition)', 'role': 'assistant'}]