Assertion $(A) :-$ Parasympathetic neural signals decrease the cardiac output.
Reason $(R) :-$ Parasympathetic neural signals decrease the rate of heartbeat and the speed of conduction of action potentials.

• A
  Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$.
• B
  Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$.
• C
  $A$ is correct but $R$ is incorrect.
• D
  Both $A$ and $R$ are incorrect.