( ( These substances ) ( ( can ( be ( chemical ( ( elements or ) compounds ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS substances)) (VP (MD can) (VP (VB be) (NP (JJ chemical) (NNS elements) (CC or) (NNS compounds)))) (. .)))
These substances can be chemical elements or compounds.
(ROOT (S (S (NP (NN Element)) (VP (VBZ is) (NP (NP (DT the) (JJ basic) (NN chemical) (NN building) (NN block)) (PP (IN of) (NP (NN matter)))))) (: ;) (S (NP (PRP it)) (VP (VBZ is) (NP (DT the) (JJS simplest) (NN chemical) (NN substance)))) (. .)))