Which statement regarding change in synaptic strength due to neuromodulation is$$FALSE$?$

$$

a$.$ The origin of the change can be presynaptic via alteration in the number of neurotransmitter molecules released.

b$.$ The origin of the change can be postsynaptic by altering the response of the postsynaptic cell to the neurotransmitters.

c$.$ The origin of the change can be presynaptic but does not involve a change in the number of neurotransmitter molecules released.

d$.$ The size of the postsynaptic potential can be affected by the activity of a third neuron.