Which of the following is NOT a monosaccharide?

The correct choice is D, as sucrose is a disaccharide, not a monosaccharide. Monosaccharides are the simplest form of carbohydrates and consist of single sugar molecules. Examples of monosaccharides include glucose, fructose, and galactose, all of which are foundational building blocks for more complex carbohydrates.

Sucrose, on the other hand, is composed of two monosaccharides: glucose and fructose linked together. This means that while glucose, fructose, and galactose can exist independently as single units, sucrose requires the combination of two such units to form a larger structure. Understanding the difference between these types of carbohydrates is crucial for applications in nutrition and culinary medicine, where the role and impact of sugars on health are important considerations.