$\mathrm{CO}_{2}$ Generated in the Tissues Is Carried in Venous Blood Primarily

Multiple Choice

$\mathrm{CO}_{2}$ generated in the tissues is carried in venous blood primarily as

A) $\mathrm{CO}_{2}$ in the plasma
B) $\mathrm{H}_{2} \mathrm{CO}_{3}$ in the plasma
C) $\mathrm{HCO}_{3}{ }^{-}$ in the plasma
D) $\mathrm{CO}_{2}$ in the red blood cells (RBCs)
E) carboxyhemoglobin in the RBCs