( I ( ( learned ( that ( plants ( ( give us ) ( oxygen ( to breathe ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP I)) (VP (VBD learned) (SBAR (IN that) (S (NP (NNS plants)) (VP (VBP give) (NP (PRP us)) (NP (NN oxygen) (S (VP (TO to) (VP (VB breathe))))))))) (. .)))
I learned that plants give us oxygen to breathe.
(ROOT (S (NP (NN Oxygen) (NN gas)) (VP (VBZ is) (VP (VBN given) (PRT (RP off)) (PP (IN by) (NP (NNS plants))))) (. .)))