( It ( gives ( off ( explosive ( oxygen ( gas C. ) ) ) ) ) )
(ROOT (S (NP (PRP It)) (VP (VBZ gives) (PP (IN off) (NP (JJ explosive) (NN oxygen) (NN gas) (NNP C.))))))
It gives off explosive oxygen gas C.
(ROOT (S (NP (NN Oxygen) (NN gas)) (VP (VBZ is) (VP (VBN given) (PRT (RP off)) (PP (IN by) (NP (NNS plants))))) (. .)))