Answer
c. Ions flowing directly through protein channels from presynaptic to postsynaptic cell.
This is a characteristic of electrical synapses, not of chemical synapses.
Work Step by Step
At electrical synapses, the cells are electrically connected and ions flow directly between presynaptic cell and post synaptic cell. This is not the case at chemical synapses. At chemical synapses there is a "lake of fluid" between the presynaptic and the postsynaptic cells. Communication across the synapse is through the medium of chemical neurotransmitters like acetylcholine, dopamine, norepinephrine, glutamate, and aspartate.
