( ( In ( combination ( with ( volatile ( organic compounds ) ) ) ) ) ( , ( ( NO X ) ( ( ( form ozone ) ( in ( ( the presence ) ( of sunlight ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (NP (NN combination)) (PP (IN with) (NP (JJ volatile) (JJ organic) (NNS compounds))))) (, ,) (NP (DT NO) (NNP X)) (VP (VBP form) (NP (NN ozone)) (PP (IN in) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (NN sunlight)))))) (. .)))
In combination with volatile organic compounds, NO X form ozone in the presence of sunlight.
(ROOT (S (NP (NN Ozone)) (VP (VBZ is) (NP (NP (DT a) (NN compound)) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (EX there)) (VP (VBZ is) (VP (VBG sparking) (NP (JJ electrical) (NN equipment))))))))) (. .)))