( ( Acid precipitation ) ( ( is ( caused ( when ( ( ( the burning ) ( of ( fossil fuels ) ) ) ( ( emits ( sulfur dioxide ) ) ( into ( the atmosphere ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Acid) (NN precipitation)) (VP (VBZ is) (VP (VBN caused) (SBAR (WHADVP (WRB when)) (S (NP (NP (DT the) (NN burning)) (PP (IN of) (NP (JJ fossil) (NNS fuels)))) (VP (VBZ emits) (NP (NN sulfur) (NN dioxide)) (PP (IN into) (NP (DT the) (NN atmosphere)))))))) (. .)))
Acid precipitation is caused when the burning of fossil fuels emits sulfur dioxide into the atmosphere.
(ROOT (S (NP (DT The) (NN element) (NN sulfur)) (VP (VBZ is) (VP (VBN released) (PP (IN into) (NP (DT the) (NN atmosphere))) (PP (IN by) (NP (NP (DT the) (NN burning)) (PP (IN of) (NP (JJ fossil) (NNS fuels))))))) (. .)))