The exchange of gases $(O_2 \text{ and } CO_2)$ in a mammal takes place in:

Match the Column-$I$ with Column-$II$ regarding the partial pressures of gases ($PO_2$ and $PCO_2$) in different respiratory sites:

Column-$I$	Column-$II$
$A$. Alveoli	$i$. $0.3 \ mmHg \ PCO_2$
$B$. Deoxygenated blood	$ii$. $45 \ mmHg \ PCO_2$
$C$. Atmospheric air	$iii$. $104 \ mmHg \ PO_2$
$D$. Tissue	$iv$. $40 \ mmHg \ PO_2$

$PCO_{2}$ is higher in tissues due to

Exchange of gases in lungs occurs through

People living at sea level have around $5$ million $RBC$ per cubic millimeter of their blood,whereas those living at an altitude of $5400$ metres have around $8$ million. This is because at high altitude:

During oxygen transport,the oxyhaemoglobin at the tissue level liberates oxygen to the cells because in tissue: