( ( ( Almost ( 80 percent ) ) ( of ( the atmosphere ) ) ) ( ( is ( nitrogen gas ) ) . ) )
(ROOT (S (NP (NP (RB Almost) (CD 80) (NN percent)) (PP (IN of) (NP (DT the) (NN atmosphere)))) (VP (VBZ is) (NP (NN nitrogen) (NN gas))) (. .)))
Almost 80 percent of the atmosphere is 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))))) (. .)))