This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pathology
[{'content': 'At a constant blood flow, an increase in the number of perfused capillaries improves the exchange between blood and tissue because of \nSelect and explain. \nA. Greater surface area for the diffusion of molecules, B. Faster flow velocity of plasma and red blood cells in capillaries, C. Increased permeability of the microvasculature, D. Decreased concentration of chemicals in the capillary blood', 'role': 'user'}, {'content': 'Answer: A \nExplanation: .', 'role': 'assistant'}]