Select the correct option:
$(1)$ The pericardium is a double-layered membrane surrounding the heart.
$(2)$ The $SA$ node has a higher rate of impulse generation compared to the $AV$ node.

• A
  Only $(1)$ is correct.
• B
  Only $(2)$ is correct.
• C
  Both $(1)$ and $(2)$ are correct.
• D
  Both $(1)$ and $(2)$ are incorrect.