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
An increase in which of the following parameters will shift the O2 dissociation curve to the left: 
Select and explain. 
A. Temperature, B. Paial pressure of CO2, C. 2,3 DPG concentration, D. Oxygen affinity of hemoglobin
D: Oxygen affinity of hemoglobin
Answer: D: Oxygen affinity of hemoglobin 
Explanation: D i.e. Oxygen affinity of hemoglobin