$A$-Leaves originate from shoot apical meristem and are arranged in an acropetal order.
$R$-They are the most important vegetative organ for photosynthesis.

• A
  $A$ and $R$ are both correct and $R$ is the correct explanation of $A$.
• B
  $A$ and $R$ are both correct but $R$ is not the correct explanation of $A$.
• C
  $A$ is correct and $R$ is incorrect.
• D
  $A$ is incorrect and $R$ is correct.