The difference between the effects of stimulant drugs and depressant drugs is that stimulant drugs increase the level of glutamate, serotonin, dopamine, and norepinephrine, while depressant drugs:
a) Deplete the effects of GABA.
b) Compete the effects of GABA.
c) Damage the effects of GABA.
d) Enhance the effects of GABA.