( ( Oxygen ( ( A gas ) ( that ( ( ( ( exists naturally ) ( in ( the atmosphere ) ) ) and ) ( is ( ( ( produced ( by plants ) ) ( during photosynthesis ) ) ( that ( ( ( humans and ) ( other animals ) ) breathe ) ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB Oxygen) (NP (NP (DT A) (NN gas)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBZ exists) (ADVP (RB naturally)) (PP (IN in) (NP (DT the) (NN atmosphere)))) (CC and) (VP (VBZ is) (VP (VBN produced) (PP (IN by) (NP (NNS plants))) (PP (IN during) (NP (NN photosynthesis))) (SBAR (IN that) (S (NP (NP (NNS humans)) (CC and) (NP (JJ other) (NNS animals))) (VP (VB breathe))))))))))) (. .)))
Oxygen A gas that exists naturally in the atmosphere and is produced by plants during photosynthesis that humans and other animals breathe.
(ROOT (S (NP (NNP Oxygen)) (VP (VBZ is) (VP (VBN made) (PP (IN by) (NP (NP (NNS trees)) (CC and) (NP (JJ other) (NNS plants)))) (PP (IN during) (NP (NN photosynthesis))))) (. .)))