Which of the following is classified as a hallucinogenic drug?

LSD, or lysergic acid diethylamide, is classified as a hallucinogenic drug because it significantly alters perception, mood, and cognitive processes. Hallucinogens can lead to experiences such as visual or auditory distortions and changes in thought processes, often referred to as "trips." This drug affects serotonin receptors in the brain, leading to these profound changes in sensory perception and consciousness.

In contrast, opium, codeine, and morphine are classified as opioid drugs. These substances primarily act as analgesics, providing pain relief. While they can induce feelings of relaxation and mild euphoria, they do not typically cause the sensory distortions associated with hallucinogens. Thus, while opium, codeine, and morphine have their own significant effects, they do not share the same classification as LSD, which is specifically associated with hallucinogenic experiences.