( ( The disaccharides ) ( ( ( are sometimes ) ( ( ( grouped ( with ( the ( simpler polysaccharides ) ) ) ) ( -LRB- ( ( usually ( those ( ( made up ) ( of ( ( three or ) ( four ( simple ( sugar units ) ) ) ) ) ) ) ) -RRB- ) ) ) ( to ( form ( ( a class ) ( of ( carbohydrates ( called ( the oligosaccharides ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS disaccharides)) (VP (VBP are) (ADVP (RB sometimes)) (VP (VBN grouped) (PP (IN with) (NP (DT the) (JJR simpler) (NNS polysaccharides))) (PRN (-LRB- -LRB-) (S (ADVP (RB usually)) (NP (DT those)) (VP (VBD made) (PRT (RP up)) (PP (IN of) (NP (NP (CD three)) (CC or) (NP (CD four) (JJ simple) (NN sugar) (NNS units)))))) (-RRB- -RRB-)) (S (VP (TO to) (VP (VB form) (NP (NP (DT a) (NN class)) (PP (IN of) (NP (NP (NNS carbohydrates)) (VP (VBN called) (NP (DT the) (NNS oligosaccharides))))))))))) (. .)))
The disaccharides are sometimes grouped with the simpler polysaccharides (usually those made up of three or four simple sugar units) to form a class of carbohydrates called the oligosaccharides.
(ROOT (S (NP (RB Double) (NNS sugars)) (VP (VBP are) (VP (VBN called) (NP (NNS disaccharides)))) (. .)))