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: Physiology
[{'content': 'Which of the following causes maximal cerebral vasodilation: \nSelect and explain. \nA. Hypercarbia, B. Hypoxia, C. Lactic Acidosis, D. Exercise', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Hypercarbia', 'role': 'assistant'}]