( Coal ( ( is ( ( our ( largest source ) ) ( of ( energy ( for ( producing electricity ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Coal)) (VP (VBZ is) (NP (NP (PRP$ our) (JJS largest) (NN source)) (PP (IN of) (NP (NP (NN energy)) (PP (IN for) (S (VP (VBG producing) (NP (NN electricity))))))))) (. .)))
Coal is our largest source of energy for producing electricity.
(ROOT (S (NP (NNP Coal)) (VP (VBZ is) (NP (NP (DT the) (NN source)) (PP (IN of) (NP (JJS most) (NN electricity))))) (. .)))