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 is TRUE regarding physiological changes in brain during exercise \nSelect and explain. \nA. Blood flow is decreased, B. Blood flow is increased, C. Blood flow remains unaltered, D. Blood flow initially increases and then decreases', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]