$A.$ In mosses,vegetative reproduction occurs by budding.
$R.$ In mosses,the spore-producing sporophyte stage is responsible for asexual reproduction.

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