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
Which of the following is QT interval? 
Select and explain. 
A. A, B. B, C. C, D. D
B: B
Answer: B: B 
Explanation: 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.