( ( In petroleum ) ( , ( sulfur ( ( is ( ( found ( ( ( in ( ( a variety ) ( of ( complex ( organic compounds ) ) ) ) ) and ) ( in ( natural gas ) ) ) ) ( as ( hydrogen sulfide ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NN petroleum))) (, ,) (NP (NN sulfur)) (VP (VBZ is) (VP (VBN found) (PP (PP (IN in) (NP (NP (DT a) (NN variety)) (PP (IN of) (NP (JJ complex) (JJ organic) (NNS compounds))))) (CC and) (PP (IN in) (NP (JJ natural) (NN gas)))) (PP (IN as) (NP (NN hydrogen) (NN sulfide))))) (. .)))
In petroleum, sulfur is found in a variety of complex organic compounds and in natural gas as hydrogen sulfide.
(ROOT (S (NP (NNP Hydrogen) (NNP sulfide)) (VP (VBZ is) (NP (NP (DT a) (ADJP (JJ noxious) (CC and) (JJ toxic)) (NN gas)) (VP (VBN produced) (PP (IN from) (S (VP (VBG decaying) (NP (JJ organic) (NN matter)))))) (SBAR (WHNP (WDT that)) (S (VP (VBZ contains) (NP (NN sulfur))))))) (. .)))