( ( Elemental carbon ) ( ( is ( of ( ( very low ) toxicity ) ) ) . ) )
(ROOT (S (NP (JJ Elemental) (NN carbon)) (VP (VBZ is) (PP (IN of) (NP (ADJP (RB very) (JJ low)) (NN toxicity)))) (. .)))
Elemental carbon is of very low toxicity.
(ROOT (S (NP (NP (DT The) (JJ main) (NN advantage)) (PP (IN of) (NP (NN urea)))) (VP (VBZ is) (NP (PRP$ its) (ADJP (RB very) (JJ low)) (NN toxicity))) (. .)))