Assertion $(A)$: In $Volvox$,the zygote undergoes meiosis to form four haploid cells before germination.
Reason $(R)$: $Volvox$ exhibits a haplontic life cycle.

• 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.