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: Anaesthesia
[{'content': 'Most potent cerebral vasodilator is \nSelect and explain. \nA. B blocker, B. Nitro-glycerine, C. Hyper carbia, D. Nitroprusside', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Hyper carbia', 'role': 'assistant'}]