Ventricular fibrillation occurs when:

A. the ventricles become the primary pacemaker for the heart, resulting in a rapid and irregular ventricular rhythm.
B. the ventricles quiver rather than contract normally, while organized atrial contractions continue as normal.
C. cardiac cells in the ventricles fail to completely repolarize, resulting in a decreased in ventricular automaticity.
D. many different cells in the heart depolarize independently rather than in response to an impulse from the SA node.