( ( ( ( ( ( People ( with asthma ) ) ( have ( ( acute episodes ) ( when ( ( ( the air ) ( in ( ( their ( air passages ) ) ( in ( their lungs ) ) ) ) ) ( get narrower ) ) ) ) ) ) , ) and ) ( breathing ( becomes ( more difficult ) ) ) ) . )
(ROOT (S (S (NP (NP (NNS People)) (PP (IN with) (NP (NN asthma)))) (VP (VBP have) (NP (NP (JJ acute) (NNS episodes)) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NN air)) (PP (IN in) (NP (NP (PRP$ their) (NN air) (NNS passages)) (PP (IN in) (NP (PRP$ their) (NNS lungs)))))) (VP (VBP get) (ADJP (JJR narrower)))))))) (, ,) (CC and) (S (NP (NN breathing)) (VP (VBZ becomes) (ADJP (RBR more) (JJ difficult)))) (. .)))
People with asthma have acute episodes when the air in their air passages in their lungs get narrower, and breathing becomes more 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))))))))) (. .)))