Statement $S$: In the primary stage of sewage treatment,physical particle matter is removed from water through filtration and sedimentation.
Reason $R$: Through sedimentation,soil or small pebbles are removed.

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