Which of the following carbohydrates is a true monosaccharide?

Galactose is classified as a true monosaccharide because it consists of a single sugar unit, which means it cannot be hydrolyzed into smaller carbohydrate molecules. Monosaccharides are the simplest form of carbohydrates and include other examples like glucose and fructose. Galactose, specifically, is an essential component of lactose, the sugar found in milk.

In contrast, maltose and sucrose are disaccharides, meaning they are composed of two monosaccharide units linked together. Maltose is formed from two glucose molecules, while sucrose consists of glucose and fructose. Cellulose, on the other hand, is a complex carbohydrate and a polysaccharide made up of many glucose molecules linked together, forming the structural component of plant cell walls. Due to its structure, cellulose cannot be classified as a monosaccharide. Thus, galactose stands out as the only option that meets the definition of a true monosaccharide.