( ( The ( small intestine ) ) ( ( is ( where ( ( most ( chemical digestion ) ) ( takes place ) ) ) ) . ) )
(ROOT (S (NP (DT The) (JJ small) (NN intestine)) (VP (VBZ is) (SBAR (WHADVP (WRB where)) (S (NP (JJS most) (NN chemical) (NNS digestion)) (VP (VBZ takes) (NP (NN place)))))) (. .)))
The small intestine is where most chemical digestion takes place.
(ROOT (S (PP (IN In) (NP (DT the) (NN body))) (, ,) (NP (NN chemical) (NN digestion)) (ADVP (RB mainly)) (VP (VBZ takes) (NP (NP (NN place)) (PP (IN in) (NP (DT the) (JJ small) (NN intestine))))) (. .)))
In the body, chemical digestion mainly takes place in the small intestine.