Assertion $(A)$: Fungi are either parasitic or saprophytic.
Reason $(R)$: Some fungi obtain nutrients from living organisms,while others obtain them from decaying organic matter.

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