( ( ( ( ( ( ( ( ( ( Wind , ) biomass ) , ) geothermal ) , ) solar ) , ) and ) ( hydropower resources ) ) ( generally ( ( are ( thought ( to ( have ( ( less ( environmental impact ) ) ( than ( fossil fuels ) ) ) ) ) ) ) ; ) ) )
(ROOT (S (NP (NP (NN Wind)) (, ,) (NP (NNS biomass)) (, ,) (NP (NN geothermal)) (, ,) (NP (JJ solar)) (, ,) (CC and) (NP (NN hydropower) (NNS resources))) (ADVP (RB generally)) (VP (VBP are) (VP (VBN thought) (S (VP (TO to) (VP (VB have) (NP (NP (JJR less) (JJ environmental) (NN impact)) (PP (IN than) (NP (JJ fossil) (NNS fuels))))))))) (: ;)))
Wind, biomass, geothermal, solar, and hydropower resources generally are thought to have less environmental impact than fossil fuels;
(ROOT (S (NP (NP (NNP Solar)) (CC and) (NP (NN wind))) (VP (VBP are) (ADVP (RB still)) (ADJP (JJ expensive)) (PP (VBN compared) (PP (TO to) (NP (JJ fossil) (NNS fuels))))) (. .)))