( ( The lungs ) ( ( ( improve ( the ( gaseous exchange ) ) ) ( within ( ( the alveolus ) ( helping ( ( ( the intake ) ( of ( ( ( oxygen and ) expulsion ) ( of ( carbon dioxide ) ) ) ) ) ( which ( is ( by diffusion ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS lungs)) (VP (VBP improve) (NP (DT the) (JJ gaseous) (NN exchange)) (PP (IN within) (NP (NP (DT the) (NNS alveolus)) (VP (VBG helping) (NP (NP (DT the) (NN intake)) (PP (IN of) (NP (NP (NN oxygen) (CC and) (NN expulsion)) (PP (IN of) (NP (NN carbon) (NN dioxide))))) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (PP (IN by) (NP (NN diffusion))))))))))) (. .)))
The lungs improve the gaseous exchange within the alveolus helping the intake of oxygen and expulsion of carbon dioxide which is by diffusion.
(ROOT (S (NP (NP (DT The) (NNS lungs)) (PP (IN of) (NP (NNS mammals)))) (VP (VBP are) (ADJP (JJ unique) (PP (IN in) (S (VP (VBG having) (NP (NNS alveoli))))))) (. .)))