Which of the following drugs is a CNS stimulant?

Adderall is classified as a central nervous system (CNS) stimulant primarily because it contains a combination of amphetamine salts, which work by increasing the levels of neurotransmitters in the brain, particularly dopamine and norepinephrine. This mechanism enhances alertness, attention, and energy levels, which are key characteristics of stimulant medications.

In contrast, the other options represent different classes of medications that do not act as CNS stimulants. Oxybutynin chloride is primarily an anticholinergic used to treat overactive bladder; folic acid is a vitamin essential for DNA synthesis and does not influence CNS activity as a stimulant; and buspirone hydrochloride is an anxiolytic that helps manage anxiety but does not have stimulant properties. The defining characteristics of Adderall as a CNS stimulant make it the correct choice in this scenario.