Assertion $(A)$: Death is a meaningful event.
Reason $(R)$: Death limits the number of individuals of each species and returns the materials of the body,formed by life elements,back to the environment.

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