( It ( ( ( is ( in ( the duodenum ) ) ) ( that ( ( most digestion ) ( takes place ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBZ is) (PP (IN in) (NP (DT the) (NN duodenum))) (SBAR (IN that) (S (NP (JJS most) (NNS digestion)) (VP (VBZ takes) (NP (NN place)))))) (. .)))
It is in the duodenum that most digestion takes place.
(ROOT (S (NP (JJS Most) (NNS digestion)) (VP (VBZ is) (VP (VBN completed) (PP (IN in) (NP (DT the) (NN duodenum))))) (. .)))