To solve this problem, we need to understand what the QRS complex in a standard ECG represents. Let's analyze the components of an ECG:$\newline \bullet$An ECG (Electrocardiogram) is a graphical representation of the electrical activity of the heart.$\newline \bullet$The main components of an ECG are the P wave, QRS complex, and T wave.$\newline \bullet$The P wave represents the depolarization of the atria (auricles).$\newline \bullet$The QRS complex represents the depolarization of the ventricles.$\newline \bullet$The T wave represents the repolarization of the ventricles.$\newline$Now, let's match the QRS complex with the correct option:$\newline \bullet$The QRS complex corresponds to the depolarization of the ventricles.$\newline$Therefore, the correct option is Option 2: Depolarisation of ventricles.