Which of the following is associated with 'All-or-none' law?

Once threshold intensity is reached, a full-fledged action potential is produced. Fuher increases in the intensity of a stimulus produce no increment or other change in the action potential as long as the other experimental conditions remain constant. The action potential fails to occur if the stimulus is subthreshold in magnitude, and it occurs with constant amplitude and form regardless of the strength of the stimulus if the stimulus is at or above threshold intensity. The action potential is therefore all-or-none in character. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 4. Excitable Tissue: Nerve. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.