Which of the following represents ventricular depolarization on ECG?

P wave which represents atrial depolarization. The QRS complex represents ventricular depolarization and the ST-T-U complex (ST segment, T wave, and U wave) represents ventricular repolarization. The J point is the junction between the end of the QRS complex and the beginning of the ST segment. Atrial repolarization (ST and T) is usually too low in amplitude to be detected, but it may become apparent in conditions such as acute pericarditis and atrial infarction.