Which statements about oxidation of monosaccharides are true?

• A. :I, II, IV
• B. II, III, IV
• C. I, III, IV
• D. I, II, III, IV

Answer: (D)

Monosaccharide oxidation can target different parts of the molecule and under different conditions you get distinct products. Oxidizing the aldehyde group at the top carbon (C1 in aldoses) turns it into a carboxyl group, giving aldonic acids (for example, glucose becomes gluconic acid). If instead you oxidize the terminal primary alcohol group (the CH2OH on carbon 6), you form uronic acids. If both ends are oxidized under stronger conditions, you get aldaric acids. Under even harsher, strong-oxidant conditions, the sugar can be cleaved into smaller fragments.

If the statements describe all these valid outcomes—aldonic, uronic, and aldaric acids, plus possible fragmentation under strong oxidation—then each statement reflects a real oxidation path. That’s why choosing the option that includes all of them makes sense: all four possibilities are true in the context of monosaccharide oxidation. For concrete examples, glucose forms gluconic acid (aldonic), then glucuronic acid (uronic), then glucaric acid (aldaric), while strong oxidants can break the sugar into smaller pieces.