Which enzyme is present in $RBC$s and plasma to catalyse the given reaction: $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons H^+ + HCO_3^-$?

If $ppCO_2$ is high and pH is low,then it will result in:
$i$. increase in affinity of haemoglobin for $O_2$
$ii$. decrease in affinity of haemoglobin for $O_2$
$iii$. oxygen dissociation curve shifts to left
$iv$. causes release of $O_2$ for diffusion into tissue cells
$v$. $H^+$ and $HCO_3^-$ ions combine to form carbonic acid

Body tissues obtain $O_2$ from hemoglobin. The dissociation of oxyhemoglobin in the tissues is primarily caused by which of the following conditions?

Bulk of carbon dioxide $(CO_2)$ released from body tissues into the blood is present as

How many oxygen molecules can one hemoglobin molecule carry?

The concentration of carbonic acid does not increase in the blood due to the presence of which of the following?