This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart: Normal Electrocardiogram, Subject name: Physiology
QRS complex is due to - 
Select and explain. 
A. Ventricular repolarization, B. Atrial depolarization, C. Conduction through AV node, D. Ventricular depolarization
D: Ventricular depolarization
Answer: D: Ventricular depolarization 
Explanation: Ans. is "d" i.e., Ventricular depolarization Event of ECGCauseP-waveAtrial depolarizationQRS complexVentricular depolarizationTwaveVentricular repolarizationPR intervalRepresents time taken by impulse to travel from SA node to ventricle (Atrial depolarization and AV conduction)QT intervalDuration of full ventricular contraction (Ventricular depolarization + Repolarization)