Final answer:
Ventricles repolarize during the T wave on an ECG. This part of the ECG represents the return of the ventricles to their resting state after contraction.
Step-by-step explanation:
In an electrocardiogram (ECG), ventricles repolarize during the T wave. The ECG features five prominent points: the P wave, the QRS complex, and the T wave. The small P wave represents atrial depolarization, followed by atrial contraction. The large QRS complex signifies ventricular depolarization, masking the atrial repolarization. Finally, the T wave indicates the repolarization of the ventricles. It is essential to understand that during the T wave, the ventricles are returning to their resting state in preparation for the next cardiac cycle.