The correct option is B Complex QRS - one complete pulse
P wave is the contraction of the atria.
By counting the number of QRS complexes that occur in a given time period, one can determine the heart beat rate of an individual. The QRS complex represents the depolarization of the ventricles, which initiates the ventricular contraction.
T wave represents the repolarization ( relaxation of ventricles ) of the ventricles.