What is the primary mechanism responsible for the exchange of gases in the lungs?

Partial pressure (in $mm \ Hg$) of oxygen and carbon dioxide at different parts involved in diffusion in comparison to those in the atmosphere. Identify $A$ and $B$ and choose the correct option accordingly.

Gas	Atmospheric Air	Alveoli
$O_{2}$	$159$	$A$
$CO_{2}$	$0.3$	$B$

$A$: Diffusion of carbon dioxide is $20$ times faster than oxygen.
$R$: It is due to difference in partial pressure as well as solubility of diffusing gases.

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	$iv$. $40 \ mmHg \ PO_2$

Select the correct option for the shape of guard cells in stomata.

	Stomata of Monocots	Stomata of Dicots
$A$.	Bean-shaped	Dumbbell-shaped
$B$.	Dumbbell-shaped	Bean-shaped
$C$.	Bean-shaped	Bean-shaped
$D$.	Dumbbell-shaped	Dumbbell-shaped

How much $CO_2$ is delivered to the alveoli by every $100 \;ml$ of deoxygenated blood (in $;ml$)?