Final answer:
Molecules A, B, and C in a molecule ABC that is a polysaccharide must be monosaccharides, which are compounds. Polysaccharides are polymers made from these monosaccharides linked by glycosidic bonds, hence the correct answer is C) Compounds.
Step-by-step explanation:
If molecule ABC is a polysaccharide, molecules A, B, and C, which compose it, must be monosaccharides. Polysaccharides are long chains of monosaccharides (simple sugars) linked by glycosidic bonds. Since polysaccharides are polymers of monosaccharides, the correct answer to the question is not A) Elements, B) Atoms, or D) Isotopes, as all of these are too simple and do not represent the repeating units within a polysaccharide. The suitable choice would be C) Compounds, as monosaccharides such as glucose, fructose, or galactose are compounds made up of carbon, hydrogen, and oxygen.
Monosaccharides are classified based on the number of carbons they contain, such as trioses (3 carbons), tetroses (4 carbons), pentoses (5 carbons), and hexoses (6 carbons). They serve as the building blocks for the synthesis of more complex carbohydrates like polysaccharides. Examples of these complex carbohydrates or polysaccharides include starch, glycogen, cellulose, and chitin, which can consist of hundreds to thousands of these monosaccharide units.