What is a hallucinogen?

A hallucinogen is defined as a psychoactive agent that significantly alters perceptions, thoughts, and emotions. These substances can lead to profound changes in sensory perceptions, such as visual or auditory hallucinations, mood swings, and altered thought processes. This makes option B the most accurate description of hallucinogens.

The other choices describe different categories of substances. The first choice refers to stimulants, which typically energize and suppress appetite. The third choice describes stimulants as well, focusing on physical performance enhancement. The last choice pertains to depressants, which are known for producing calming effects and relaxation. Each of these options highlights different classes of drugs and their effects, but they do not capture the unique characteristics or effects of hallucinogens.