$P$ - Assertion: Circulatory system is present in Annelids.
$Q$ - Reason: Circulatory system is absent in Aschelminthes.

• A
  $P$ (Assertion) and $Q$ (Reason) are both true,and $P$ is the correct explanation of $Q$.
• B
  $P$ (Assertion) and $Q$ (Reason) are both true,but $P$ is not the correct explanation of $Q$.
• C
  $P$ (Assertion) is true and $Q$ (Reason) is false.
• D
  $P$ (Assertion) is false and $Q$ (Reason) is true.