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
[{'content': 'Which of the following is QT interval? \nSelect and explain. \nA. A, B. B, C. C, D. D', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) QT intervalPR interval (A)120-200msec and represents spread of impulse from SAN to AV nodeRR interval (C)Inversely related to heart rateQT interval (B)400-430 msec and represents ventricular depolarization and repolarization.', 'role': 'assistant'}]