In the Transport Of $\mathrm{CO}_{2}$ From the Tissues to the Lungs, Which of the Following

In the transport of $\mathrm{CO}_{2}$ from the tissues to the lungs, which of the following occurs in venous blood?

A) Conversion of $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ to $\mathrm{H}^{+}$ and $\mathrm{HCO}_{3}{ }^{-}$ in the red blood cells (RBCs)
B) Buffering of $\mathrm{H}^{+}$ by oxyhemoglobin
C) Shifting of $\mathrm{HCO}_{3}^{-}$ into the RBCs from plasma in exchange for $\mathrm{Cl}^{-}$
D) Binding of $\mathrm{HCO}_{3}{ }^{-}$ to hemoglobin
E) Alkalinization of the RBCs