Which of the following substances is considered a narcotic?

A narcotic is defined as a substance that dulls the senses, alleviates pain, and often induces sleep or stupor. Opium is classified as a narcotic because it is derived from the poppy plant and contains natural compounds, including morphine and codeine, which have significant pain-relieving properties. These compounds interact with specific receptors in the brain to produce their effects.

In contrast, methamphetamine and cocaine are stimulants; they increase activity and alertness, rather than dulling the senses or inducing sleep. LSD is classified as a hallucinogen, primarily affecting perception and mood, leading to hallucinations and altered states of consciousness, rather than providing pain relief or sedation.

Opium's historical and medical significance as a narcotic aligns it with the classic definition, making it the correct choice among the substances listed.