The diagram given here is the standard ECG of a normal person. The P-wave represents the

Step-by-step solution

In ECG, P-wave represents the depolarisation of atria, which leads to the contraction of both atria. T-wave represents the return of ventricles from excited to normal state. The QRS complex represents the depolarisation of the ventricles, which initiates ventricular contraction. The contraction starts shortly after Q and marks the beginning of systole.