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
True about Hb dissociation curve: 
Select and explain. 
A. Acidosis shifts O2 dissociation curve to right, B. Increased CO2 shifts the curve to left, C. Hypoxia shifts curve to left, D. 2,3 DPG has no effect on curve
A: Acidosis shifts O2 dissociation curve to right
Answer: A: Acidosis shifts O2 dissociation curve to right 
Explanation: Oxygen-hemoglobin dissociation curve is shifted to right in the following conditions: 

Decrease in partial pressure of oxygen.
 Increase in partial pressure of carbon dioxide (Bohr effect).
Increase in hydrogen ion concentration and decrease in pH (acidity). 
Increased body temperature. 
Excess of 2,3-diphosphoglycerate (DPG) in RBC. It is also called 2,3-biphosphoglycerate (BPG). DPG is a byproduct in Embden-Meyer-hof pathway of carbohydrate metabolism. It combines with β-chains of hemoglobin. In conditions like muscular exercise and in high attitude, the DPG increases in RBC. So, the oxygen-hemoglobin dissociation curve shifts to right to a great extent.