6) Humans are unable to digest cellulose fibers but can digest starch because humans have enzymes that can digest only A) peptide bonds but not glycosidic bonds B) 1,4 glycosidic linkage but not 1,4 glycosidic linkages. C) nonpolar covalent bonds but not polar covalent bonds D) 1,4 glycosidic linkage but not 1,4 glycosidic linkages. E) ionic bonds but not covalent bonds