Which one of the following is a non-reducing sugar?

The correct answer is Option (2) → Sucrose

• A reducing sugar has a free aldehyde or ketone group (or a ring that opens to give one), so it reduces Fehling’s solution and Tollens’ reagent.

• In sucrose the linkage joins C1 of α-D-glucose to C2 of β-D-fructose: the aldehyde carbon of glucose and the ketone carbon of fructose. Both reducing groups are used up, so sucrose is a non-reducing sugar.

Why the other options are incorrect

Option (1) Glucose — Incorrect. Glucose is an aldohexose; its ring opens in solution to give a free –CHO group.

Option (3) Fructose — Incorrect. Fructose is a ketohexose, and every monosaccharide is a reducing sugar.

Option (4) Maltose — Incorrect. Its two α-D-glucose units are joined C1 to C4, so C1 of the second unit stays free and maltose is a reducing sugar.

NCERT (2026-27 edition):
Classification of Carbohydrates – “… All those carbohydrates which reduce Fehling’s solution and Tollens’ reagent are referred to as reducing sugars.”

Disaccharides – “In disaccharides, if the reducing groups of monosaccharides i.e., aldehydic or ketonic groups are bonded, these are non-reducing sugars, e.g., sucrose.”