What type of molecules are galactose, D-glucose, and fructose examples of?

Galactose, D-glucose, and fructose are examples of carbohydrates. More specifically, they are monosaccharides, which are the simplest form of carbohydrates. These molecules are classified as sugars and are the building blocks for more complex carbohydrates.

Monosaccharides like these have the same molecular formula (C6H12O6) but differ in structure and sweetness, which classifies them as isomers of one another. However, the question seeks a broader classification. Carbohydrates encompass both monosaccharides like galactose, D-glucose, and fructose, as well as disaccharides and polysaccharides, making "carbohydrates" the more accurate answer.

While isomers refer to molecules that have the same formula but different structures (which is true for the sugars mentioned), the term "carbohydrates" correctly identifies the category to which they belong as a whole. Therefore, focusing on their classification as carbohydrates provides a clearer understanding of their role in biology and nutrition compared to just considering them as isomers.