Final answer:
The QT interval reflects the time between the end of ventricular contraction and the beginning of ventricular recovery.
Step-by-step explanation:
The correct answer is d. QT interval. The QT interval reflects the time between the end of ventricular contraction and the beginning of ventricular recovery. It represents the duration of ventricular depolarization and repolarization.
In an ECG, the QRS complex represents the depolarization of the ventricles and the T wave represents the repolarization of the ventricles. The QT interval includes both these waveforms and provides important information about the duration of ventricular electrical activity.
For example, a prolonged QT interval can indicate an increased risk of ventricular arrhythmias, such as Torsades de Pointes. On the other hand, a shortened QT interval may be seen in certain conditions, such as hypercalcemia.