This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
The T wave on an ECG tracing represents which of the events in the cardiac cycle? 
Select and explain. 
A. Atrial depolarization, B. Atrial repolarization, C. Ventricular depolarization, D. Ventricular repolarization
D: Ventricular repolarization
Answer: D: Ventricular repolarization 
Explanation: The T wave represents ventricular repolarization and is longer in duration than depolarization (i.e., conduction of the repolarization wave is slower than the wave of depolarization). The P wave represents the wave of depolarization that spreads from the SA node throughout the atria, and is usually 0.08 to 0.1 seconds (80-100 ms) in duration. The QRS complex represents ventricular depolarization. The Q-T interval represents the time for both ventricular depolarization and repolarization to occur, and therefore roughly estimates the duration of an average ventricular action potential.