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: Physiology
[{'content': 'Which of the following has the greatest effect on the ability of blood to transport oxygen? \nSelect and explain. \nA. Capacity of the blood to dissolve oxygen, B. Amount of hemoglobin in the blood, C. pH of plasma, D. CO2 content of red blood cells', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The amount of O2 in the blood is determined by the amount of dissolved O2, the amount of hemoglobin in the blood, and the affinity of the hemoglobin for O2.', 'role': 'assistant'}]