Final answer:
Cellulose and starch are composed of the same glucose monomers but have different structures due to the orientation of the glycosidic linkages, resulting in different biological roles.(Option d)
Step-by-step explanation:
The substances composed of the same monomer units, just arranged differently, are cellulose and starch. Both cellulose and starch are polysaccharides that consist of glucose monomers. However, they differ in the orientation of the glycosidic linkages; cellulose has a linear chain of glucose molecules, while starch (which includes amylose and amylopectin) typically has branched chains.
This results in their differing roles in biological organisms, with cellulose serving mainly as a structural component in plant cell walls and starch being used primarily for energy storage in plants.