Step 1: Understanding lactose.
Lactose is a disaccharide composed of glucose and galactose. It is the primary sugar found in milk.
It provides energy and is also important for the absorption of calcium.
Step 2: Analyzing other options.
- (1) Glucose: Incorrect. Glucose is found in many foods but is not the main sugar in milk.
- (2) Fructose: Incorrect. Fructose is found in fruits, not in milk.
- (4) Galactose: Incorrect. Galactose is part of lactose, but on its own, it is not found in milk.
Step 3: Conclusion.
Therefore, the correct answer is (3) Lactose, as it is the main sugar in milk.