sentence2_structure: Caffeine and alcohol<>are<>two examples of a psychoactive
sentence1: Socially accepted, legal psychoactive substances (alcohol, nicotine, caffeine), on the other hand, are not qualify as drugs for the aims of the following analysis.
sentence2: Caffeine and alcohol are two examples of a psychoactive.
question: Caffeine and alcohol are two examples of what type of drug?