Answer: D. Carbohydrates
Step-by-step explanation:
Cellulose is a kind of carbohydrate. It is a linear polysaccharide. It is composed of monosaccharides of glucose units. The glucose units are linked by the beta acetal linkage. Humans are incapable of digesting cellulose because they do not posses enzyme which can digest the beta acetal linkage. It is a major component of the plant cell wall.