Final answer:
The VA node is not a component of the normal cardiac conduction system, which includes the SA node, AV node, Bundle of His, and Purkinje fibers.
Step-by-step explanation:
The correct answer to the question is D. VA node. The normal excitation pathway of the heart begins at the sinoatrial (SA) node, which acts as the heart's natural pacemaker, dictating the rhythm by which the heart beats. From the SA node, the electrical impulse moves through the internodal pathways to the atrioventricular (AV) node. After a slight delay here, to allow the atria to complete pumping blood into the ventricles, the impulse is then transmitted to the Bundle of His (atrioventricular bundle), and from there it continues down the bundle branches to the Purkinje fibers, which then stimulate the ventricular myocardium to contract. The VA node is not a component of the cardiac conduction system; thus, it is not a normal excitation pathway.