Which of the following is an example of a monosaccharide?

Glucose is classified as a monosaccharide because it is the simplest form of carbohydrate, consisting of a single sugar unit. Monosaccharides are the basic building blocks of more complex carbohydrates and cannot be hydrolyzed into simpler sugars. They serve as fundamental sources of energy and can be directly utilized by cells.

In contrast, starch, lactose, and maltose are not monosaccharides. Starch is a polysaccharide, which means it comprises many glucose units linked together, making it a more complex carbohydrate used by plants for energy storage. Lactose is a disaccharide formed from two monosaccharides, glucose and galactose, and requires enzymatic breakdown for the body to utilize the sugars it contains. Similarly, maltose is also a disaccharide made from two glucose units.

Thus, glucose stands out as the correct answer, as it is the only option that fits the definition of a monosaccharide, while the others are either disaccharides or polysaccharides.