Classifying carbohydrates requires combining two criteria: how many sugar units they release on hydrolysis, and the nature and number of carbon atoms in the unit. A carbohydrate that cannot be hydrolysed to anything simpler is by definition a monosaccharide. The description specifies a polyhydroxy aldehyde, which places it among aldoses, and the presence of six carbon atoms makes it a hexose. Combining these, the compound is an aldohexose monosaccharide, glucose being the classic example. A reducing disaccharide is ruled out because disaccharides yield two monosaccharide units on hydrolysis, contradicting the stated non-hydrolysable nature. A ketohexose would contain a ketone rather than an aldehyde group, so that classification conflicts with the polyhydroxy aldehyde description, and labelling it a polysaccharide is also wrong. A trisaccharide would hydrolyse into three units. This applies the NCERT classification scheme based on hydrolysis behaviour and functional group. As a consistency check, an aldohexose has the molecular formula C6H12O6 with one aldehyde and five hydroxyl-bearing carbons, which is exactly consistent with a single non-hydrolysable polyhydroxy aldehyde of six carbons.