Assertion $(A)$: Maize is included in the class Monocotyledonae.
Reason $(R)$: This class does not contain any orders.

• 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, but $R$ is false.
• D
  $A$ is false, but $R$ is true.