The partial pressure of $O_{2}$ and $CO_{2}$ in atmospheric air as compared to those in alveolar air is:

Gas	Alveolar Air $(X/A)$	Atmospheric Air $(Y/B)$
$pO_{2}$	$X$	$Y$
$pCO_{2}$	$A$	$B$

• A
  $X > Y$ and $A > B$
• B
  $X < Y$ and $A < B$
• C
  $X > Y$ and $A < B$
• D
  $X < Y$ and $A > B$