Which of these is a source of disaccharides?

Disaccharides are carbohydrates that are composed of two monosaccharide units linked together. Sucrose is a prime example of a disaccharide, as it consists of one glucose molecule combined with one fructose molecule. This direct chemical structure defines sucrose as a disaccharide.

In contrast, fructose, glucose, and galactose are all monosaccharides. Each of these sugars consists of a single sugar unit. They cannot be classified as disaccharides since they do not consist of two linked monosaccharide molecules. Therefore, understanding the composition and structure of carbohydrates clarifies why sucrose is correctly identified as a disaccharide, while the other options are not.