Final answer:
A monosaccharide is the simplest form of carbohydrate that cannot be hydrolyzed any further and includes sugars like glucose and fructose.
Step-by-step explanation:
The substance that cannot be hydrolyzed any further is a monosaccharide. Monosaccharides are the simplest form of carbohydrates and include glucose, fructose, and threose. They serve as the building blocks for more complex sugars such as disaccharides and polysaccharides, which can be hydrolyzed back into monosaccharides. Examples of complex carbohydrates that hydrolyze are cellulose and starch, which are polysaccharides.