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
Haemoglobin is the major buffer in blood, bicarbonate ions diffuses out of erythrocyte into plasma in exchange of: 
Select and explain. 
A. Potassium, B. Phosphate, C. Carbonic acid, D. Chloride ion
D: Chloride ion
Answer: D: Chloride ion 
Explanation: None