Disaccharides are formed by dehydration reactions between two monosaccharides.

• A. They are formed by hydrolysis
• B. They are formed by oxidation
• C. Disaccharides are formed by dehydration
• D. They are formed by polymerization

Answer: (C)

Disaccharide formation occurs through dehydration synthesis, a condensation reaction where two monosaccharides are joined by a glycosidic bond and a water molecule is removed. This removal of water links the sugars, often producing α- or β-glycosidic linkages as seen in common disaccharides like sucrose, lactose, and maltose. If water were added, hydrolysis would break that bond, yielding two monosaccharides. Oxidation would change functional groups rather than create the linkage, and polymerization would build long chains to form polysaccharides rather than just two units.