( This ( ( is ( because ( ( the ( digestive process ) ) ( actually ( begins ( ( ( ( in ( the mouth ) ) , ) not ) ( in ( ( ( the stomach ) , ) ( as ( ( is popularly ) thought ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (SBAR (IN because) (S (NP (DT the) (JJ digestive) (NN process)) (ADVP (RB actually)) (VP (VBZ begins) (PP (PP (IN in) (NP (DT the) (NN mouth))) (, ,) (RB not) (PP (IN in) (NP (NP (DT the) (NN stomach)) (, ,) (SBAR (IN as) (S (VP (VBZ is) (ADVP (RB popularly)) (VP (VBN thought)))))))))))) (. .)))
This is because the digestive process actually begins in the mouth, not in the stomach, as is popularly thought.
(ROOT (S (NP (NNP Digestion)) (VP (VBZ begins) (PP (IN in) (NP (DT the) (NN mouth)))) (. .)))