Oxygen is transported by

$CO_2$ is transported in blood primarily as:

Oxyhaemoglobin in the blood is formed when

Identify $A$ and $B$ in the given oxygen-haemoglobin dissociation curve and choose the correct option accordingly.

$I.$ 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:

Select the favourable conditions required for the formation of oxyhaemoglobin at the alveoli.