( ( ( Air ( pollution ( Basic characters ) ) ) ( of ( the ( atmosphere primary ) ) ) ) ( ( vs ( secondary pollutants ) ) ; ) )
(ROOT (S (NP (NP (NNP Air) (NN pollution) (NN Basic) (NNS characters)) (PP (IN of) (NP (DT the) (NN atmosphere) (NN primary)))) (VP (VBP vs) (NP (JJ secondary) (NNS pollutants))) (: ;)))
Air pollution Basic characters of the atmosphere primary vs secondary pollutants;
(ROOT (S (NP (NP (NNP Ash)) (SBAR (WHNP (WDT that)) (S (VP (VBZ enters) (NP (DT the) (NN air)) (PP (ADVP (RB naturally)) (IN as) (NP (NP (DT a) (NN result)) (PP (IN of) (NP (DT a) (NN volcano) (NN eruption))))))))) (VP (VBZ is) (VP (VBN classified) (PP (IN as) (NP (DT a) (JJ primary) (NN pollutant))))) (. .)))