Lactose is the correct answer. Lactose is a disaccharide sugar found in milk and dairy products. It is composed of glucose and galactose molecules. Option 1, Glucose, is a monosaccharide sugar found in many fruits, plants, and as the primary product of photosynthesis. Option 2, Fructose, is also a monosaccharide sugar found in fruits and honey. Option 3, Maltose, is a disaccharide sugar made up of two glucose molecules and is commonly found in germinated grains and malt beverages. Lactose is specifically known as milk sugar because it is abundantly present in milk and is a source of energy for infants and young animals.