( ( The ( best example ) ) ( ( is ( rain water ) ) . ) )
(ROOT (S (NP (DT The) (JJS best) (NN example)) (VP (VBZ is) (NP (NN rain) (NN water))) (. .)))
The best example is rain water.
(ROOT (S (NP (NN Rain)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (JJ liquid) (NN water))))) (. .)))