Assertion $(A):$ The body of sponges is supported by a skeleton.
Reason $(R):$ The skeleton of sponges is made up of spicules and spongin fibres.

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