This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
[{'content': 'PR interval corresponds to ECG changes as \nSelect and explain. \nA. Ventricular depolarization, B. Ventricular depolarization and atrial rcpolarization, C. Atrial depolarization and conduction through AV node, D. Ventricular repolarization', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C. i.e. (Atrial - depolarization and conduction through AV node) (551 - Ganong 22nd) (494- Ganong 23rd)ECG IntervalsIntervalNormal Durations (S)Events in the heart during intervalAverageRangePR interval0.180.12-0.20**Atrial depolarization and conduction through AV nodeQRS duration0.08to 0.10Ventricular depolarization and atrial repolarizationQT interval0.40to 0.43Ventricular depolarization plus ventricular repolarizationST interval (QT minus QRS)0.32 Ventricular repolarization* QRS complex denotes - ventricular depolarization*** The normal direction of mean QRS vector is generally said to be - 30 to + 110 on the coordinate system*** U wave - It is due to slow repolarization of papillary muscle* TP segment - It represents polarized state of whole heart* J-point - point between \'S\' wave and ST segment. It is a point of "no" electrical activity (305-A.K Jain 3rd)', 'role': 'assistant'}]