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 vinodilator \nSelect and explain. \nA. Hydralazine, B. Minoxidil, C. Nitroprusside, D. Nifedipine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ref-Katzung 10/e p173-174 Hydralazine, minoxidil and nifedipinen are primary aeriolar dilators whereas nitroprusside is a mixed Aeriolar and Venous delator therefore best answer here seems to be nitroprusside', 'role': 'assistant'}]