The oxygen dissociation curve of hemoglobin is . . . . . . .

$A$ healthy individual has $A$ grams of haemoglobin in every $B$ mL of blood. These molecules play a significant role in the transport of $C$ gases.
Choose the correct option for $A$, $B$, and $C$.

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

What percentage of $CO_2$ is transported in the form of bicarbonate in the blood (in $\%$)?

$I.$ Increased partial pressure of $O_{2}$
$II.$ Increased partial pressure of $CO_{2}$
$III.$ Increased partial pressure of $H^{+}$
$IV.$ Decreased partial pressure of $O_{2}$
All the above situations favour the dissociation of oxyhaemoglobin except:

In lungs,there is a definite exchange of ions between $RBC$ and plasma. The removal of $CO_2$ from the blood involves: