( ( ( ( ( Hydrogen Sulfide ) , ) ( ( H 2 ) S ) ) , ) ( ( ( ( ( is ( produced ( by ( ( the decay ) ( of ( organic matter ) ) ) ) ) ) , ) and ) ( then ( rises ( to ( ( the atmosphere ) ( where ( it ( ( ( oxidizes and ) forms ) ( sulfur dioxide ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Hydrogen) (NNP Sulfide)) (, ,) (NP (NP (NNP H) (CD 2)) (NP (NNP S))) (, ,)) (VP (VP (VBZ is) (VP (VBN produced) (PP (IN by) (NP (NP (DT the) (NN decay)) (PP (IN of) (NP (JJ organic) (NN matter))))))) (, ,) (CC and) (VP (ADVP (RB then)) (VBZ rises) (PP (TO to) (NP (NP (DT the) (NN atmosphere)) (SBAR (WHADVP (WRB where)) (S (NP (PRP it)) (VP (VBZ oxidizes) (CC and) (VBZ forms) (NP (NN sulfur) (NN dioxide))))))))) (. .)))
Hydrogen Sulfide, H 2 S, is produced by the decay of organic matter, and then rises to the atmosphere where it oxidizes and forms sulfur dioxide.
(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))))))) (. .)))