This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'As aerial pressure is raised and lowered during the course of a day, blood flow through the brain would be expected to \nSelect and explain. \nA. Change in the same direction as the aerial blood pressure because of the limited autoregulatory ability of the cerebral vessels, B. Change in a direction opposite the change in mean aerial pressure, C. Remain constant because cerebral vascular resistance changes in the same direction as aerial pressure, D. Fluctuate widely, as both aerial pressure and brain neural activity status change', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Brain blood flow is constant despite large changes in the aerial blood pressure because vascular resistance usually changes in the same direction as the aerial pressure and by almost the same percentage.Ref: Guyton; 13th edition', 'role': 'assistant'}]