The building units for oligosaccharides and polysaccharides are

Correct option is A

Monosaccharides are the simplest form of carbohydrates and serve as the basic building blocks for more complex sugars like oligosaccharides (2–10 monosaccharide units) and polysaccharides (more than 10 units). Common examples of monosaccharides include glucose, fructose, and galactose. Through glycosidic linkages, these simple sugars join to form complex carbohydrates such as starch, cellulose, and glycogen, which play key roles in plant structure and energy storage.