( Very ( ( low toxicity ) . ) )
(ROOT (FRAG (ADVP (RB Very)) (NP (JJ low) (NN toxicity)) (. .)))
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))) (. .)))