Considering That All Action Potentials Are Essentially the Same, How

Considering that all action potentials are essentially the same, how do we differentiate visual from auditory stimuli?

A) The amplitude of each action potential is specific for different stimuli.
B) The length of time each stimulus takes to travel to the brain varies.
C) Receptor potentials are graded.
D) Each type of sensory receptor transmits to a specific area of the brain.
E) The frequency of action potentials is characteristic of the specific neuron.