( ( Also ( like plants ) ) ( , ( they ( ( ( give off ) oxygen ) . ) ) ) )
(ROOT (S (PP (ADVP (RB Also)) (IN like) (NP (NNS plants))) (, ,) (NP (PRP they)) (VP (VBP give) (PRT (RP off)) (NP (NN oxygen))) (. .)))
Also like plants, they give off oxygen.
(ROOT (S (NP (NN Oxygen) (NN gas)) (VP (VBZ is) (VP (VBN given) (PRT (RP off)) (PP (IN by) (NP (NNS plants))))) (. .)))