Which sugar is commonly referred to as milk sugar?

Lactose is commonly referred to as milk sugar because it is the primary sugar found in milk and dairy products. Lactose is a disaccharide composed of two simpler sugars: glucose and galactose. It plays a crucial role in providing energy to infants, as it is naturally present in human milk, and it also helps facilitate the absorption of calcium and other minerals in the digestive system.

The other options represent different types of sugars that do not have the same relationship to milk. Sucrose is common table sugar and is found in many plants. Maltose, often referred to as malt sugar, is produced during the digestion of starch and can be found in malted foods and beverages. Galactose, while part of lactose, is a monosaccharide that is also found in various foods but does not specifically represent milk sugar itself. Understanding the specific role and source of each of these sugars helps clarify why lactose is uniquely identified as milk sugar.