What is the only natural source of lactose?

Lactose is a disaccharide sugar that is naturally found in milk and is the primary carbohydrate present in this substance. It is commonly referred to as milk sugar and is produced in the mammary glands of mammals. During the digestion process, lactose is broken down into glucose and galactose by the enzyme lactase. This unique presence in milk makes it the sole natural source of lactose, distinguishing it from other food sources such as honey, fruits, or eggs, which do not contain this particular sugar or can contain carbohydrates in different forms. Thus, selecting milk as the correct answer highlights its essential role in providing lactose in a natural dietary context.