( ( It ( cleans ( ( ( the air ) and ) ( ( ( purifies ( the ( respiratory system ) ) ) , ) therefore ) ) ) ) ( , ( it ( ( is ( useful ( for ( disease ( of ( the ( respiratory system ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (S (NP (PRP It)) (VP (VBZ cleans) (NP (NP (DT the) (NN air)) (CC and) (NP (NP (NNS purifies)) (NP (DT the) (JJ respiratory) (NN system)) (, ,) (ADVP (RB therefore)))))) (, ,) (NP (PRP it)) (VP (VBZ is) (ADJP (JJ useful) (PP (IN for) (NP (NP (NN disease)) (PP (IN of) (NP (DT the) (JJ respiratory) (NN system))))))) (. .)))
It cleans the air and purifies the respiratory system, therefore, it is useful for disease of the respiratory system.
(ROOT (S (NP (NNP Narrow) (NN air) (NNS passages)) (VP (VBP make) (S (VP (VBG breathing) (ADJP (JJ difficult) (RB due) (S (VP (TO to) (VP (VB respiratory) (NP (NN system) (NN disease))))))))) (. .)))