Lactose on hydrolysis gives:

\(\beta \)-D-glucose and \(\beta \)-D-galactose

The correct answer is option 4. \(\beta \)-D-glucose and \(\beta \)-D-galactose.

Lactose is a disaccharide composed of two monosaccharides: β-D-galactose and α-D-glucose. The linkage between these monosaccharides in lactose is known as a β-1,4-glycosidic bond. This bond joins the anomeric carbon atom of the glucose molecule with the hydroxyl group of the fourth carbon atom of the galactose molecule.

When lactose undergoes hydrolysis, this glycosidic bond is cleaved by the addition of a water molecule. This hydrolysis reaction breaks the bond, yielding the two constituent monosaccharides: β-D-galactose and α-D-glucose.

Importantly, the configuration of the anomeric carbon in the released monosaccharides is determined by the configuration of the original glycosidic bond. Since the glycosidic bond in lactose is β, both resulting monosaccharides, β-D-galactose and α-D-glucose, retain the β configuration after hydrolysis.

Therefore, the correct answer is option 4: \(\beta\)-D-glucose and \(\beta\)-D-galactose.