( ( This mucus ) ( ( ( ( clogs ( air passages ) ) and ) ( makes ( breathing difficult ) ) ) . ) )
(ROOT (S (NP (DT This) (NNS mucus)) (VP (VP (VBZ clogs) (NP (NN air) (NNS passages))) (CC and) (VP (VBZ makes) (S (VP (VBG breathing) (ADJP (JJ difficult)))))) (. .)))
This mucus clogs air passages and makes breathing difficult.
(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))))))))) (. .)))