ECG depicts the depolarisation and repolarisation processes during the cardiac cycle. In the ECG of a normal healthy individual one of the following waves is not represented.

1. Depolarisation of atria

2. Repolarisation of atria

3. Depolarisation of ventricles

4. Repolarisation of ventricles

Which of the following correctly explains a phase/event in cardiac cycle in a standard electrocardiogram?

1. QRS complex indicates atrial contraction.

2. QRS complex indicates ventricular contraction.

3. Time between S and T represents atrial systole.

4. P-wave indicates beginning of ventricular contraction.