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': 'Increase in P50 results in change in oxygenation curve, which is due to decrease in \nSelect and explain. \nA. pH, B. Oxygen, C. Temperature, D. CO2', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Hb-O2\xa0dissociation curve shift to left indicates more affinity of Hb to O2 and thus less delivery of O2\xa0to tissues. \nHb-O2\xa0dissociation curve shift to right indicates less affinity of Hb to O2, and thus more delivery of O2\xa0to tissues. \nWhen P50 increases, the affinity of Hb to O2 decreases, or there is a shift of the curve to the right. \nAmong the given options, the only decrease in pH causes a right shift of the curve. All others when decreased cause shifts to left.', 'role': 'assistant'}]