The correct option is B Monosaccharide
Carbohydrates are polyhydroxy aldehydes or ketones. The carbohydrates can be monosaccharides, oligosaccharides or polysaccharides. Monosaccharides are made up of single unit composed of 3 to 7 carbon atoms, e.g., glyceraldehyde, erythrose, ribose, glucose, fructose, sedoheptulose. The monosaccharides having aldehyde group are called aldose and those having ketone group are called ketose sugars.