Which of the following is a monosaccharide?

• A. Glucose
• B. Sucrose
• C. Lactose
• D. Maltose

Answer: (A)

Distinguishing monosaccharides from disaccharides is being tested here. A monosaccharide is a single sugar unit that cannot be broken into smaller sugars by hydrolysis. Glucose is a monosaccharide, serving as a primary energy source for cells. The other options are disaccharides, made of two monosaccharide units linked together: sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (two glucose molecules). Because they comprise two sugar units, they are not monosaccharides. Therefore, glucose is the correct choice.