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: Medicine
[{'content': 'The key factor in the transport of carbon dioxide as bicarbonate is - \nSelect and explain. \nA. The high solubility of CO2  in H2O, B. The presence of Hb in blood, C. The presence of carbonic anhydrase in the erythrocytes, D. The acid nature of carbon dioxide and the alkaline nature of bicarbonate', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]