( ( ( Heroin , ) ( cocaine ( , ( marijuana ( , ( nicotine ( , ( alcohol ( , ( and caffeine ) ) ) ) ) ) ) ) ) ) ( ( ( are all ) ( psychoactive drugs ) ) . ) )
(ROOT (S (NP (NP (NNP Heroin)) (, ,) (NP (NN cocaine) (, ,) (NN marijuana) (, ,) (NN nicotine) (, ,) (NN alcohol) (, ,) (CC and) (NN caffeine))) (VP (VBP are) (RB all) (NP (JJ psychoactive) (NNS drugs))) (. .)))
Heroin, cocaine, marijuana, nicotine, alcohol, and caffeine are all psychoactive drugs.
(ROOT (S (NP (NN Caffeine) (CC and) (NN alcohol)) (VP (VBP are) (NP (NP (CD two) (NNS examples)) (PP (IN of) (NP (DT a) (NN psychoactive))))) (. .)))
Caffeine and alcohol are two examples of a psychoactive.