Final answer:
The QRS complex represents ventricular depolarization and the start of ventricular systole, and typically lasts less than 0.12 second.
Step-by-step explanation:
The QRS complex is a component of the ECG tracing that represents ventricular depolarization and the beginning of ventricular systole. Ventricular systole lasts a total of 270 milliseconds, or 0.27 seconds. When measured in an ECG tracing, however, the QRS interval specifically is generally less than 0.12 second (option D). This timing works to ensure that proper cardiac function is maintained with precise coordination between atrial and ventricular contractions. It is critical to maintain this interval within the correct time frame, as any deviation (either shorter or longer) can lead to heart abnormalities.
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