This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conducting System of Hea, Subject name: Physiology
[{'content': 'Which of the following segments of the circulatory system has the highest velocity of blood flow? \nSelect and explain. \nA. Aoa, B. Aeries, C. Capillaries, D. Venules', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The velocity of blood flow within each segment of the circulatory system is inversely propoional to the total cross-sectional area of the segment. Because the aoa has the smallest total cross-sectional area of all circulatory segments, it has the highest velocity of blood flow', 'role': 'assistant'}]