This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
[{'content': 'The normal P wave is biphasic in lead \nSelect and explain. \nA. V1, B. LII, C. aVF, D. aVR', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The normal P wave in lead V1 may be biphasic with a positive component reflecting right atrial depolarization, followed by a small (<1 mm2 ) negative component reflecting left atrial depolarization. Ref Harrison 20th edition pg 1455', 'role': 'assistant'}]