$P$ (Assertion): Earthworms have a closed type of circulatory system.
$Q$ (Reason): Earthworms have hemoglobin dissolved in their blood plasma.

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