( ( The automobile ) ( ( is ( ( the ( chief source ) ) ( of ( primary ( air pollutants ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN automobile)) (VP (VBZ is) (NP (NP (DT the) (JJ chief) (NN source)) (PP (IN of) (NP (JJ primary) (NN air) (NNS pollutants))))) (. .)))
The automobile is the chief source of primary air pollutants.
(ROOT (S (NP (JJ Primary) (NNS pollutants)) (VP (VBP enter) (NP (DT the) (NN air)) (ADVP (RB directly))) (. .)))