This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory System, Subject name: Physiology
[{'content': 'Transport of carbon monoxide (CO) is diffusion limited because- \nSelect and explain. \nA. High affinity of CO for hemoglobin, B. Alveolar membrane is less permeable CO, C. CO crosses epithelial barrier slowly, D. ON exposure to air there is sudden increase in partial pressure', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. (a) High affinity of CO for hemoglobin(Ref: Ganong, 25th ed/p.640)The affinity of carbon monoxide for hemoglobin is about 210 times more than that of oxygen for hemoglobin', 'role': 'assistant'}]