A hallucinogen is a drug that affects the function of the brain by altering consciousness. This substance binds to the serotonin receptor and enhances serotonin production. There are three classes of hallucinogens, viz psychedelics, dissociatives and deliriants. Lysergic acid diethylamide(LSD), psilocybin and mescaline are psychedelic drugs that cause psychological effects. So, the correct answer is option D.