This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Electrocardiography, Subject name: Medicine
P wave in ECG is due to : 
Select and explain. 
A. Ventricular depolarization, B. Atrial repolarization, C. Ventricular repolarization, D. Atrial depolarization
D: Atrial depolarization
Answer: D: Atrial depolarization 
Explanation: Ans. (d) Atrial depolarizationECG findingSignificanceP waveAtrial DepolarizationQRSVentricular depolarizationT waveVentricular repolarizationU waveDelayed repolarization of papillary musclesPR intervalSpread of impulse from SAN to AVNST segmentIso-electric segment