The correct option is D All of the above
Carbohydrates can be monosaccharides (comprised of a single sugar unit), oligosaccharides (comprised of few sugar units) or polysaccharides (comprised of multiple sugar units). Monosaccharides are named after number of carbon atoms present in each unit, for example: a monosaccharide unit which contains three carbon atoms is called a triose sugar, having four carbon atoms is called tetrose sugar, having five carbon atoms is called pentose sugar, having six carbon atoms is called hexose sugar. Glucose is a hexose sugar. Further the sugar having aldehyde functional group are called aldoses and those having ketone group are called ketoses.