( ( ( ( ( ( The duodenum ) ( is ( ( ( only 25 ) cm ) long ) ) ) , ) but ) ( ( most ( of ( the digestion ) ) ) ( takes ( place ( in ( this region ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT The) (NN duodenum)) (VP (VBZ is) (ADVP (NP (QP (RB only) (CD 25)) (NN cm)) (RB long)))) (, ,) (CC but) (S (NP (NP (JJS most)) (PP (IN of) (NP (DT the) (NN digestion)))) (VP (VBZ takes) (NP (NP (NN place)) (PP (IN in) (NP (DT this) (NN region)))))) (. .)))
The duodenum is only 25 cm long, but most of the digestion takes place in this region.
(ROOT (S (NP (JJS Most) (NNS digestion)) (VP (VBZ is) (VP (VBN completed) (PP (IN in) (NP (DT the) (NN duodenum))))) (. .)))