( ( ( ( ( Coal ( was ( ( the ( principal ( energy source ) ) ) ( used ( to ( raise steam ) ) ) ) ) ) , ) and ) ( today ( it ( provides ( most ( of ( ( the ( electric power ) ) ( that ( is ( fundamental ( to ( ( the operation ) ( of computers ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Coal)) (VP (VBD was) (NP (NP (DT the) (JJ principal) (NN energy) (NN source)) (VP (VBN used) (S (VP (TO to) (VP (VB raise) (NP (NN steam))))))))) (, ,) (CC and) (S (NP (NN today)) (NP (PRP it)) (VP (VBZ provides) (NP (NP (JJS most)) (PP (IN of) (NP (NP (DT the) (JJ electric) (NN power)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (ADJP (JJ fundamental) (PP (TO to) (NP (NP (DT the) (NN operation)) (PP (IN of) (NP (NNS computers)))))))))))))) (. .)))
Coal was the principal energy source used to raise steam, and today it provides most of the electric power that is fundamental to the operation of computers.
(ROOT (S (NP (NNP Coal)) (VP (VBZ is) (NP (NP (DT the) (NN source)) (PP (IN of) (NP (JJS most) (NN electricity))))) (. .)))