( ( ( Air pollution ) ( from ( ( cars and ) trucks ) ) ) ( ( is ( split ( into ( primary ( and ( secondary pollution ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Air) (NN pollution)) (PP (IN from) (NP (NNS cars) (CC and) (NNS trucks)))) (VP (VBZ is) (VP (VBN split) (PP (IN into) (NP (JJ primary) (CC and) (JJ secondary) (NN pollution))))) (. .)))
Air pollution from cars and trucks is split into primary and secondary pollution.
(ROOT (S (NP (JJ Primary) (NNS pollutants)) (VP (VBP enter) (NP (DT the) (NN air)) (ADVP (RB directly))) (. .)))