( ( ( This type ) ( of pollution ) ) ( ( is ( formed ( when ( ( ( ( ( volatile ( organic compounds ) ) ( -LRB- ( VOCs -RRB- ) ) ) and ) ( ( nitrogen oxides ) ( -LRB- ( NOx -RRB- ) ) ) ) ( combine ( in ( ( the presence ) ( of ( sunlight ( and ( high temperatures ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT This) (NN type)) (PP (IN of) (NP (NN pollution)))) (VP (VBZ is) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (NP (NP (JJ volatile) (JJ organic) (NNS compounds)) (PRN (-LRB- -LRB-) (NP (NNP VOCs)) (-RRB- -RRB-))) (CC and) (NP (NP (NN nitrogen) (NNS oxides)) (PRN (-LRB- -LRB-) (NP (NNP NOx)) (-RRB- -RRB-)))) (VP (VBP combine) (PP (IN in) (NP (NP (DT the) (NN presence)) (PP (IN of) (NP (NN sunlight) (CC and) (JJ high) (NNS temperatures)))))))))) (. .)))
This type of pollution is formed when volatile organic compounds (VOCs) and nitrogen oxides (NOx) combine in the presence of sunlight and high temperatures.
(ROOT (S (NP (NNP Nitrogen)) (VP (VBZ oxide) (NP (NP (NN form)) (PRN (-LRB- -LRB-) (PRP s) (-RRB- -RRB-)) (SBAR (WHADVP (WRB when)) (S (NP (NN nitrogen) (CC and) (NN oxygen)) (VP (VBP combine) (PP (IN at) (NP (JJ high) (NNS temperatures)))))))) (. .)))