( ( The atmosphere ) ( ( is ( ( 78 % ) ( nitrogen gas ) ) ) . ) )
(ROOT (S (NP (DT The) (NN atmosphere)) (VP (VBZ is) (NP (ADJP (CD 78) (NN %)) (NN nitrogen) (NN gas))) (. .)))
The atmosphere is 78% nitrogen gas.
(ROOT (S (NP (NN Nitrogen) (NN gas)) (VP (VBZ comprises) (NP (NP (QP (RB about) (NNS three-fourths))) (PP (IN of) (NP (NP (NN earth) (POS 's)) (NN atmosphere))))) (. .)))