The figure shows blood circulation in humans with labels $A$ to $D$. Select the option which gives correct identification of label and functions of the part.

• A
  $B$ - Capillary: Thin,without muscle layer and wall is one cell layer thick.
• B
  $C$ - Vein: Thin-walled and blood flows in jerks/spurts.
• C
  $D$ - Pulmonary vein: Takes oxygenated blood to heart,$pO_2 = 95 \ mm \ Hg$.
• D
  $A$ - Artery: Thick-walled and blood flows evenly.