Which of the following statements about facilitation is FALSE?
a) Facilitation is said to have occurred when a neuron is brought closer to threshold at the initial segment of the axon.
b) Facilitation can occur by exposing a neuron to certain drugs in the extracellular fluid, such as nicotine and caffeine.
c) Facilitation can occur as a result of spatial or temporal summation.
d) All of the listed responses are false; none is true.