The sequence of electrical impulse conduction in a heartbeat is:

• A
  $AV$ node $\rightarrow$ Pacemaker $\rightarrow$ Auricles $\rightarrow$ Ventricles
• B
  Ventricle $\rightarrow$ Pacemaker $\rightarrow$ $AV$ node $\rightarrow$ Auricle
• C
  Pacemaker $\rightarrow$ Atria $\rightarrow$ $AV$ node $\rightarrow$ Ventricle
• D
  Pacemaker $\rightarrow$ $AV$ node $\rightarrow$ Atria $\rightarrow$ Ventricle