Step 1: Identify the main carbohydrate in milk.
Milk contains lactose (milk sugar), which is a disaccharide.
Step 2: Digestion (hydrolysis) of lactose.
Lactose is broken down by enzyme lactase into:
\[
\text{Lactose} \rightarrow \text{Glucose} + \text{Galactose}
\]
Step 3: Match with options.
Among options, glucose is a correct digestion product.
Final Answer:
\[
\boxed{\text{(C) glucose}}
\]