( Plants ( ( extract ( ( ( several ( of ( these elements ) ) ) , ) ( such ( as ( ( oxygen ( , ( carbon ( , ( and ( hydrogen , ) ) ) ) ) ) ( from ( ( water and ) air ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Plants)) (VP (VB extract) (NP (NP (JJ several)) (PP (IN of) (NP (DT these) (NNS elements))) (, ,) (PP (JJ such) (IN as) (NP (NP (NN oxygen) (, ,) (NN carbon) (, ,) (CC and) (NN hydrogen) (, ,)) (PP (IN from) (NP (NN water) (CC and) (NN air))))))) (. .)))
Plants extract several of these elements, such as oxygen, carbon, and hydrogen, from water and air.
(ROOT (S (PP (IN On) (NP (DT a) (JJ global) (NN scale))) (, ,) (NP (NP (NNS plants)) (CC and) (NP (JJ other) (JJ photosynthetic) (NNS organisms))) (VP (VBP have) (VP (VBN generated) (NP (NP (DT all)) (PP (IN of) (NP (NP (DT the) (NN oxygen)) (PP (IN in) (NP (DT the) (NN air)))))))) (. .)))
On a global scale, plants and other photosynthetic organisms have generated all of the oxygen in the air.