( Scientists ( ( have ( discovered ( that ( ( ( air pollution ) ( from ( burning ( of ( fossil fuels ) ) ) ) ) ( is ( ( the ( major cause ) ) ( of ( acid rain ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Scientists)) (VP (VBP have) (VP (VBN discovered) (SBAR (IN that) (S (NP (NP (NN air) (NN pollution)) (PP (IN from) (NP (NP (NN burning)) (PP (IN of) (NP (JJ fossil) (NNS fuels)))))) (VP (VBZ is) (NP (NP (DT the) (JJ major) (NN cause)) (PP (IN of) (NP (JJ acid) (NN rain))))))))) (. .)))
Scientists have discovered that air pollution from burning of fossil fuels is the major cause of acid rain.
(ROOT (S (NP (JJ Acid) (NN rain)) (VP (MD may) (VP (VB be) (VP (VBN caused) (PP (IN by) (NP (NN air) (NN pollution)))))) (. .)))