( ( The ( human brain ) ) ( ( is ( ( the ( ( most complex ) system ) ) ( on earth ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ human) (NN brain)) (VP (VBZ is) (NP (NP (DT the) (ADJP (RBS most) (JJ complex)) (NN system)) (PP (IN on) (NP (NN earth))))) (. .)))
The human brain is the most complex system on earth.
(ROOT (S (NP (DT The) (NN brain)) (VP (VBZ is) (NP (NP (DT the) (ADJP (RBS most) (JJ complex)) (NN organ)) (PP (IN in) (NP (DT the) (JJ human) (NN body))))) (. .)))