The rate of firing of the postsynaptic neuron depends on the amount of input it receives from the presynaptic neuron. a. excitation b. inhibition c. equalizing d. both excitation and inhibition

The postsynaptic potential is the membrane potential, which takes place in the neuron present post synapsis (after the chemical synapse). The presynaptic neuron releases neurotransmitter, which causes the firing in the postsynaptic neurons.  

The firing of the post synaptic neuron depends on the excitation and inhibition inputs received from the presynaptic neuron. The firing is the resultant of the summation of excitatory and inhibitory potential. In case, the excitatory potential is greater than inhibitory potential, the post synaptic neuron would be excited. in case, inhibitory potential is greater than excitatory potential, then the post synaptic neuron would be inhibited.  

Hence, the correct answer is option d.