How is $70\%$ of carbon dioxide transported by the blood to the lungs?

$A$ graph plotted between $pO_{2}$ and the percentage saturation of $Hb$ with $O_{2}$ is known as:

$A$: Major part of carbon dioxide is transported in the form of sodium bicarbonate.
$R$: $0.3 \; ml$ of carbon dioxide is transported per $100 \; ml$ of blood in dissolved state in plasma of blood.

Approximately $70\%$ of carbon dioxide absorbed by the blood is transported to the lungs:

Which factors affect the dissociation of $O_{2}$ from $Hb$?

$CO_{2}$ diffuses into ...$A$... and forms $HCO_{3}^{-}$ and $H^{+}$. At the ...$B$... site where $pCO_{2}$ is low, the reaction proceeds in the opposite direction.
Thus, $CO_{2}$ is trapped as ...$C$... at the tissue level and transported to alveoli is released out as ...$D$...
Select the right choice for $A, B, C$ and $D$ to complete the given $NCERT$ statement.