( ( Oxygen ( -LRB- ( ( O 2 ) -RRB- ) ) ) ( ( is ( ( an example ) ( of ( a ( noble gas ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Oxygen)) (PRN (-LRB- -LRB-) (NP (NNP O) (CD 2)) (-RRB- -RRB-))) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (DT a) (JJ noble) (NN gas))))) (. .)))
Oxygen (O 2 ) is an example of a noble gas.
(ROOT (S (NP (NNP Neon)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (JJ noble) (NN gas))))) (. .)))