Which of the following is NOT a type of disaccharide?

The correct choice is D, as glucose is a monosaccharide, not a disaccharide. Disaccharides are carbohydrates composed of two monosaccharide units linked together by a glycosidic bond. Lactose, maltose, and sucrose all fit this definition, as they are each made up of two monosaccharide units:

• Lactose consists of glucose and galactose.

• Maltose is formed from two glucose molecules.

• Sucrose is composed of glucose and fructose.

In contrast, glucose is the simplest form of sugar, serving as a primary energy source in the body, and stands alone without any other monosaccharide linked to it. Thus, it is classified as a monosaccharide, distinguishing it from the other options provided.