( Plants ( ( ( ( give off ) ( oxygen ( for animals ) ) ) ( to ( breathe in ) ) ) . ) )
(ROOT (S (NP (NNS Plants)) (VP (VBP give) (PRT (RP off)) (NP (NP (NN oxygen)) (PP (IN for) (NP (NNS animals)))) (S (VP (TO to) (VP (VB breathe) (PRT (RP in)))))) (. .)))
Plants give off oxygen for animals to breathe in.
(ROOT (S (NP (NN Oxygen) (NN gas)) (VP (VBZ is) (VP (VBN given) (PRT (RP off)) (PP (IN by) (NP (NNS plants))))) (. .)))