In which of the following aspects do the pteridophytes $Equisetum$ and $Selaginella$ differ?

• A
  $Equisetum$ is non-flowering and $Selaginella$ is flowering.
• B
  $Equisetum$ is flowering and $Selaginella$ is non-flowering.
• C
  $Equisetum$ is heterosporous and $Selaginella$ is homosporous.
• D
  $Equisetum$ is homosporous and $Selaginella$ is heterosporous.