( Coal ( ( is ( a ( clean ( energy source ) ) ) ) ? ) )
(ROOT (SBARQ (WHNP (WP Coal)) (SQ (VBZ is) (NP (DT a) (JJ clean) (NN energy) (NN source))) (. ?)))
Coal is a clean energy source?
(ROOT (S (S (NP (NNP Coal)) (VP (VBZ is) (ADJP (JJ nonrenewable)))) (, ,) (CC and) (S (NP (DT the) (NN sun)) (VP (VBZ is) (ADJP (JJ renewable) (SBAR (S (VP (VBZ is) (SBAR (WHADVP (WRB how)) (S (NP (NP (NN coal)) (CC and) (NP (DT the) (NN sun))) (VP (VBP compare) (PP (IN as) (NP (NP (NNS sources)) (PP (IN of) (NP (NN energy)))))))))))))) (. .)))