Erythrocytes function in the transport of CO₂ by

A) containing carbonic anhydrase, which catalyzes the interconversion of CO₂ and bicarbonate.
B) containing hemoglobin, which binds CO₂ to the iron portion.
C) containing hemoglobin, which binds CO₂ to the protein portion.
D) both containing carbonic anhydrase and binding CO₂ to the iron portion.
E) both containing carbonic anhydrase and binding CO₂ to the protein portion.