If a Neuron Only Fires at Full Strength How Is

If a neuron only fires at full strength how is it possible for us to perceive the difference between a weak stimulus and a strong stimulus?

A) It is the number of neurons firing, and their rate of fire, that determines this.
B) The brain must determine from other factors how strong or weak a stimulus is.
C) Memory of past similar stimuli determines this.
D) We still don't know this. It is being researched.