Read the passage carefully and answer the questions.

Carbohydrates such as cane sugar, glucose, starch etc. belong to a class of naturally occurring organic compounds. Structurally these are polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis. Carbohydrates which are sweet in taste are called sugars. Theses sugars can be reducing or non-reducing. Monosaccharides cannot be hydrolyzed to simpler units whereas Oligosaccharides yield two to ten monosaccharide units on hydrolysis. Polysaccharides yield large number of monosaccharide units on hydrolysis. This class of biomolecules is essential for living systems as they serve as storage molecules in plants and animals. In addition, they provide raw materials for important industries like furniture, textiles, paper, lacquers and breweries. Two aldopentose form important constituents of nucleic acids. Carbohydrates are also called saccharides (Greek: sakcharon which means sugar). Sugar which is used in household and in milk also comes under this class of biomolecules.

Reducing sugars respond to

Both Tollen's and Fehling's reagent

The correct answer is Option (3) → Both Tollen's and Fehling's reagent

Tollens’ Reagent – Reducing sugars give a positive silver mirror test with Tollens’ reagent because they contain a free aldehyde or ketone group that can be oxidized.

Fehling’s Reagent – Reducing sugars also reduce Fehling’s solution to form a brick-red precipitate of cuprous oxide, again due to the presence of a free carbonyl group.

Both Tollens’ and Fehling’s Reagent – This is the correct option because reducing sugars react with both reagents as each test detects the reducing (free carbonyl) group in sugars.

Schiff’s Reagent – Schiff’s reagent is mainly used for detecting aldehydes in general organic compounds and is not the standard confirmatory test for reducing sugars in carbohydrate chemistry.