Which of the following is an example of a CNS stimulant?

Cocaine is classified as a central nervous system (CNS) stimulant due to its ability to increase alertness, attention, and energy levels. It works by enhancing the levels of certain neurotransmitters in the brain, specifically dopamine, which contributes to feelings of euphoria and heightened energy. Stimulants like cocaine often lead to increased heart rate, elevated blood pressure, and can produce feelings of excitement or alertness, making it a quintessential example of a CNS stimulant.

In contrast, the other options revolve around substances that do not primarily stimulate the CNS in the same manner. Barbiturates are sedative-hypnotic drugs that depress the CNS, primarily used for their calming effects. Anti-depressants can have various effects depending on their class, with some having stimulant properties but generally used to stabilize mood rather than stimulate. Non-barbiturates, which include various sedatives and anxiolytics, also act to depress the CNS rather than stimulate it. This emphasis on the stimulating effects of cocaine clarifies why it is the correct answer in this context.