Which of the following represents the complete chemical reaction for the bicarbonate buffer system?


A. CO2 + H2O <-> HCO3- + H+ <->H2CO3
B. CO2 + H2O <-> H2CO3 <-> HCO3- + H+
C. CO2 + H2O <-> HCO3- + H+
D. H2CO3 <-> HCO3- + H+
E. H2CO3 <-> CO2 + H2O <-> HCO3- + H+