Monosaccharides are the simplest carbohydrates and cannot be hydrolyzed further. Examples: Glucose Fructose Galactose In contrast: Polysaccharides (e.g., starch) and disaccharides (e.g., sucrose) can be hydrolyzed into smaller sugar units. Oligosaccharides consist of a few monosaccharide units.
Final Answer: \[ \boxed{\text{Monosaccharides}} \]