Final answer:
The statement that the P wave indicates the beginning of cardiac depolarization is true, as it represents the depolarization of the atria on an ECG.
Step-by-step explanation:
The statement "The P wave shows the beginning of cardiac depolarization" is true. The P wave on an electrocardiogram (ECG) represents the depolarization of the atria, which is the electrical activity that initiates the contraction of the atrial heart muscle. After the P wave and a brief delay, the atria contract, and this is followed by the QRS complex, which signifies the depolarization of the ventricles. The T wave on the ECG reflects the repolarization of the ventricles. Depolarization is crucial for cardiac muscle contraction and is an essential aspect of the heart's electrical and mechanical activity.