Hallucinogens are drugs which:

Correct option is A

Correct Answer: (a)
Explanation:
Hallucinogens (e.g., LSD, psilocybin) primarily alter perception, thought, and mood — causing hallucinations and sensory distortions.
Information Booster:
Hallucinogens act on serotonin and other neurotransmitter systems.
Effects include altered sense of time, synesthesia, and visual/auditory hallucinations.
They are psychedelics, not primarily analgesic or CNS depressants.
Some substances (e.g., opioids) act as painkillers; others (e.g., barbiturates) suppress CNS — different drug classes.
Medical and legal status varies; some are under study for psychiatric therapy.
Additional Information (Incorrect Options):
(b) Some stimulants increase CNS activity, but hallucinogens mainly alter perception.
(c) Analgesics (e.g., opioids) act as pain killers — not a primary property of hallucinogens.
(d) CNS depressants (e.g., benzodiazepines) suppress activity — not a defining feature of hallucinogens.