( It ( ( is ( ( a ( colourless liquid ) ) ( with ( ( a ( strong ( odor characteristic ) ) ) ( of ( alkyl sulfides ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (NP (NP (DT a) (JJ colourless) (NN liquid)) (PP (IN with) (NP (NP (DT a) (JJ strong) (NN odor) (NN characteristic)) (PP (IN of) (NP (JJ alkyl) (NNS sulfides))))))) (. .)))
It is a colourless liquid with a strong odor characteristic of alkyl sulfides.
(ROOT (S (NP (JJ Strong) (NN odor)) (VP (VBZ helps) (S (NP (DT some) (NNS animals)) (VP (VB defend) (NP (PRP themselves)) (PP (IN against) (NP (NNS predators)))))) (. .)))
Strong odor helps some animals defend themselves against predators.