Hi Jeff, All these words and phrases are OK in proper context. As nouns, human(s) and human being(s) are virually interchangeable, with the former perhaps used more in contrast with the 'lower' animals while the latter may be used more in discussing our humanity. As an adjective, only 'human' will work, of course (as it is, I suppose, in 'human being', actually, even though we do not use the counter-term 'non-human being') So: 'we are human'-- 'human' is a predicate adjective, a subject complement.
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