The $pCO_2$ of inspired air is . . . . . . $mm \ Hg$ during external respiration.

Name the primary site of exchange of gases in our body?

What will be the $pO_{2}$ and $pCO_{2}$ in atmospheric air as compared to alveoli?

Maximum amount of oxygen is exchanged from the blood in the . . . . . . .

What is the value of $pO_2$ in alveoli and tissues respectively?

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
$O_{2}$	$159$	$A$
$CO_{2}$	$0.3$	$B$