This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Maximum reservoir of blood \nSelect and explain. \nA. Large vein, B. Aoa, C. Hea, D. Capillaries', 'role': 'user'}, {'content': "Answer: A \nExplanation: At rest, at least 50% of the circulating blood volume is in the systemic veins, 12% is in the hea cavities, and 18% is in the low-pressure pulmonary circulation. Only 2% is in the aoa, 8% in the aeries, 1% in the aerioles, and 5% in the capillaries Ref: Ganong's Review of Medical Physiology Twenty-Third Edition Page No:543", 'role': 'assistant'}]