$S -$ Statement: The cisternae of the Golgi apparatus have a diameter of $5.0$ to $10 \, \mu m$.
$R -$ Reason: Each stack contains $2$ to $4$ tubules.

• 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
  $S$ and $R$ are both false.