Which one is the correct route through which the cardiac impulse travels in the heart?

• A
  $SA$ node $\to$ Purkinje fibres $\to$ Bundle of His $\to$ $AV$ node $\to$ Heart muscles
• B
  $AV$ node $\to$ $SA$ node $\to$ Purkinje fibres $\to$ Bundle of His $\to$ Heart muscles
• C
  $AV$ node $\to$ Bundle of His $\to$ $SA$ node $\to$ Purkinje fibres $\to$ Heart muscles
• D
  $SA$ node $\to$ $AV$ node $\to$ Bundle of His $\to$ Purkinje fibres $\to$ Heart muscles