Brain central nervous system human being nerve tissue neurons organize the parts of this body system in the correct order according to the levels of organization in a multicellular organism, simplest to most complex.. a) human being - central nervous system - brain - nerve tissue - neurons b) brain - neurons - nerve tissue - central nervous system - human being c) neurons - nerve tissue - brain - central nervous system - human being d) nerve tissue - neurons - brain - central nervous system - human being