( Often ( , ( ( this gas ) ( ( is ( ( a ( noble ( ( -LRB- ( or ( inert -RRB- ) ) ) gas ) ) ) ( -LRB- ( ( ( ( ( such ( as ( Neon ( , ( Argon ( , ( or Krypton ) ) ) ) ) ) ) , ) or ) ( ( a combination ) ( of ( noble gases ) ) ) ) -RRB- ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Often)) (, ,) (NP (DT this) (NN gas)) (VP (VBZ is) (NP (NP (DT a) (ADJP (JJ noble)) (PRN (-LRB- -LRB-) (CC or) (ADJP (JJ inert)) (-RRB- -RRB-)) (NN gas)) (PRN (-LRB- -LRB-) (NP (NP (JJ such)) (PP (IN as) (NP (NNP Neon) (, ,) (NNP Argon) (, ,) (CC or) (NNP Krypton))) (, ,) (CC or) (NP (NP (DT a) (NN combination)) (PP (IN of) (NP (JJ noble) (NNS gases))))) (-RRB- -RRB-)))) (. .)))
Often, this gas is a noble (or inert) gas (such as Neon, Argon, or Krypton, or a combination of noble gases).
(ROOT (S (NP (NNP Neon)) (VP (VBZ is) (NP (NP (DT an) (NN example)) (PP (IN of) (NP (JJ noble) (NN gas))))) (. .)))