This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Microbiology
The chloride shift occurs rapidly and is essentially completes in 
Select and explain. 
A. 1 second, B. 2 seconds, C. 5 seconds, D. 60 seconds
A: 1 second
Answer: A: 1 second 
Explanation: Chloride ShiftSince the rise in the HCO3- content of red cells is much greater than that in plasma as the blood passes through the capillaries, about 70% of the HCO3- formed in the red cells enters the plasma.The excess HCO3- leaves the red cells in exchange for Cl-, a process mediated by Band 3, a major membrane protein. This exchange is called the chloride shift. Because of it, the Cl- content of the red cells in venous blood is therefore significantly greater than in aerial blood. The chloride shift occurs rapidly and is essentially completes in 1 second.