Which term refers to a simple sugar that serves as a primary energy source?

• A. Fructose
• B. Glucose
• C. Lactose
• D. Galactose

Answer: (B)

The main idea here is identifying which simple sugar is used by the body as its primary energy source. Glucose is that sugar because cells break it down through glycolysis to produce ATP, the main energy currency of the body. The brain relies heavily on glucose for fuel, underscoring its role as the universal energy source for cells. Fructose, while a simple sugar, is processed mainly in the liver and isn’t used as readily available energy by all tissues. Lactose is a disaccharide that has to be split into glucose and galactose before it can be used for energy. Galactose is another monosaccharide but is typically converted into glucose in the liver rather than serving as the direct primary energy source. So glucose best fits the description.