Which type of carbohydrate molecule contains an aldehyde group?

The correct answer identifies an aldehyde group as a key feature of certain carbohydrate molecules known as aldoses. Aldoses are a type of monosaccharide that have the aldehyde functional group (-CHO) at one end of their carbon chain. This characteristic distinguishes aldoses from other types of sugars, such as ketoses, which contain a ketone group (C=O) instead.

In the context of carbohydrate classification, aldoses play a crucial role in various biochemical processes, serving as fundamental building blocks for more complex sugars and carbohydrates. Their structural feature allows them to participate in important reactions, contributing to the energy metabolism within living organisms.

The other options do not carry the functional group described. Ketoses contain a ketone group, disaccharides consist of two monosaccharides joined by a glycosidic bond, and polysaccharides are made up of long chains of monosaccharides connected through glycosidic linkages. None of these options present the aldehyde configuration characteristic of aldoses.