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
All of the following factors influence Oxygen haemoglobin dissociation curve, except 
Select and explain. 
A. Chloride ion conc., B. CO2 tension, C. Temperature, D. 2,3 DPG
A: Chloride ion conc.
Answer: A: Chloride ion conc. 
Explanation: None