( ( Breathing air ) ( ( is ( necessary ( for ( keeping ( ( ( ( ( humans -LRB- ) and ) ( many animals ) ) -RRB- ) alive ) ) ) ) ) . ) )
(ROOT (S (NP (VBG Breathing) (NN air)) (VP (VBZ is) (ADJP (JJ necessary) (PP (IN for) (S (VP (VBG keeping) (S (NP (NP (NNS humans)) (-LRB- -LRB-) (CC and) (NP (JJ many) (NNS animals)) (-RRB- -RRB-)) (ADJP (JJ alive)))))))) (. .)))
Breathing air is necessary for keeping humans (and many animals) alive.
(ROOT (S (NP (DT An) (JJ underwater) (NN spider)) (VP (VBZ uses) (NP (JJ shiny) (NN air) (NN bubble) (S (VP (TO to) (VP (VP (VB breathe)) (CC and) (VP (VB keep) (ADJP (JJ alive)))))))) (. .)))