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
[{'content': 'Wave (Arrow) shown in the Phtograph is due to \nSelect and explain. \nA. Atrial depolarization, B. Atrial repolarization, C. Ventricular depolarization, D. Ventricular repolarization', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Atrial depolarization (Wave shown: p-wave in ECG)', 'role': 'assistant'}]