This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
The duration of a ventricular myocyte action potential is 
Select and explain. 
A. Approximately twice as long as the relative refractory period, B. As long in duration as the QRS complex, C. Nearly as long as the QT interval, D. Twice as long in skeletal muscle
C: Nearly as long as the QT interval
Answer: C: Nearly as long as the QT interval 
Explanation: The diagram depicts the relationship between the electrocardiogram (ECG) recorded on the surface of the body and the duration of a single ventricular myocyte action potential. The duration of the ventricular myocyte refractory period is nearly as long as the action potential, approximately 300 msec. The QRS complex of an ECG represents the electrical potential on the surface of the body produced by the wave of depolarization as it spreads through the ventricle and as each myocyte depolarizes (phase 0). The T wave represents ventricular repolarization (phase 3 in each myocyte). Note that the ST segment occurs during the plateau phase.