Regarding renal handling of bicarbonate ion, which is INCORRECT?

• A. small size of bicarbonate ion affects reabsorption
• B. reabsorption is reciprocally related to chloride ion reabsorption in proximal tubule
• C. most reabsorption occurs in proximal tubule
• D. reabsorption requires carbonic anhydrase
• E. reabsorption is decreased by ECF expansion