Action Potentials Are Described as Being 'All-Or-None

Action potentials are described as being 'all-or-none'. This property means that ______.

A) action potentials do not vary in size dependent upon the size of the stimulus
B) an axon can only fire one action potential at a time
C) for an action potential to be triggered all of the sodium channels in the membrane need to open
D) if a sensory neuron experiences a stimulus below the threshold potential it will produce a small action potential