Which of the following are the three main classes of carbohydrates?

The three main classes of carbohydrates are indeed monosaccharides, disaccharides, and polysaccharides. Monosaccharides are the simplest form of carbohydrates, consisting of single sugar molecules like glucose and fructose. These serve as the building blocks for more complex carbohydrates. Disaccharides are composed of two monosaccharides linked together, such as sucrose and lactose, and they provide a quick source of energy. Polysaccharides are large, complex molecules made up of many monosaccharide units joined together, such as starch, glycogen, and cellulose, which serve various roles including energy storage and structural support in plants.

The other options listed do not pertain to carbohydrates. The second choice refers to types of biomolecules crucial for various metabolic processes, the third choice lists essential nutrients required by the body, and the fourth choice mentions types of lipids. Each of these categories plays important roles in biology but does not represent classes of carbohydrates. Thus, recognizing the correct classes of carbohydrates helps in understanding their structure and function within biological systems.