Which Phase of the Cardiac Cycle Is Absent If There $\mathrm{P}$

Which phase of the cardiac cycle is absent if there is no $\mathrm{P}$ wave on the electrocardiogram (ECG) ?

A) Atrial systole
B) Isovolumetric ventricular contraction
C) Rapid ventricular ejection
D) Reduced ventricular ejection
E) Isovolumetric ventricular relaxation
F) Rapid ventricular filling
G) Reduced ventricular filling