Which of the following are reducing sugars?(A) Sucrose(B) Lactose(C)…

The correct answer is Option (3) → B, C and D only

A reducing sugar reduces Fehling’s solution and Tollens’ reagent; it needs a free aldehydic or ketonic group.

(A) Sucrose — Not a reducing sugar. The reducing groups of its glucose and fructose units are bonded to each other, so none is free.

(B) Lactose — A reducing sugar. A free aldehyde group can form at C1 of its glucose unit.

(C) Maltose — A reducing sugar. One of its two glucose units keeps a free reducing group.

(D) Galactose — A reducing sugar. It is a monosaccharide (one of the two units of lactose), and every monosaccharide is a reducing sugar.

NCERT (2026-27 edition):
10.1.1 Classification of Carbohydrates – “The carbohydrates may also be classified as either reducing or non-reducing sugars. All those carbohydrates which reduce Fehling’s solution and Tollens’ reagent are referred to as reducing sugars. All monosaccharides whether aldose or ketose are reducing sugars.”

10.1.3 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. On the other hand, sugars in which these functional groups are free, are called reducing sugars, for example, maltose and lactose.”

“(iii) Lactose: It is more commonly known as milk sugar since this disaccharide is found in milk. It is composed of β-D-galactose and β-D-glucose.”