Which of the following is an example of a depressant?

Alcohol is classified as a depressant because it primarily acts on the central nervous system to produce a calming effect. This class of substances tends to lower the level of bodily or mental activity, leading to relaxation and drowsiness. When consumed, alcohol enhances the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) while simultaneously inhibiting the release of excitatory neurotransmitters, which results in the suppression of neural activity.

In contrast, caffeine is a stimulant that increases alertness and energy levels, while cocaine is a powerful stimulant that elevates mood and increases heart rate. Nicotine, though it has calming effects in some contexts, primarily acts as a stimulant that increases arousal and concentration. Therefore, alcohol stands out as a typical example of a depressant, illustrating its distinct role in influencing the nervous system compared to other substances listed.