( Certainly ( ( ( the ( most ( conspicuous reason ) ) ) ( for ( ( the investment ) ( in ( renewable ( energy sources ) ) ) ) ) ) ( ( is ( to ( cut ( ( the ( opportunity cost ) ) ( associated ( with ( ( using oil ) ( as ( a ( domestic ( energy source ) ) ) ) ) ) ) ) ) ) ) . ) ) )
(ROOT (S (ADVP (RB Certainly)) (NP (NP (DT the) (RBS most) (JJ conspicuous) (NN reason)) (PP (IN for) (NP (NP (DT the) (NN investment)) (PP (IN in) (NP (JJ renewable) (NN energy) (NNS sources)))))) (VP (VBZ is) (S (VP (TO to) (VP (VB cut) (NP (NP (DT the) (NN opportunity) (NN cost)) (VP (VBN associated) (PP (IN with) (S (VP (VBG using) (NP (NN oil)) (PP (IN as) (NP (DT a) (JJ domestic) (NN energy) (NN source)))))))))))) (. .)))
Certainly the most conspicuous reason for the investment in renewable energy sources is to cut the opportunity cost associated with using oil as a domestic energy source.
(ROOT (S (NP (NNP Oil)) (VP (VBZ is) (NP (NP (DT the) (ADJP (RBS most) (RB commonly) (VBN used)) (NN source)) (PP (IN of) (NP (NP (NN energy)) (PP (IN in) (NP (DT the) (NN world))))))) (. .)))