Study the following in $Pheretima$.
$I.$ Dorso-intestinal blood vessels
$II.$ External intestinal plexus
$III.$ Internal intestinal plexus
$IV.$ Ventro-intestinal blood vessel
Arrange the blood vessels in the correct sequence of blood flow from the ventral blood vessel to the dorsal blood vessel.
The correct sequence is:

• A
  $IV \rightarrow II \rightarrow III \rightarrow I$
• B
  $III \rightarrow I \rightarrow II \rightarrow IV$
• C
  $II \rightarrow III \rightarrow IV \rightarrow I$
• D
  $IV \rightarrow II \rightarrow I \rightarrow III$