$A$: Meiosis occurs only in diploid $(2n)$ cells.
$R$: Meiosis-$I$ is known as reductional division.

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