The basis of classification of governments as unitary and federal lies in the relationship between the Centre and States. In a unitary government, power and authority are concentrated in the central government, which makes decisions and holds control over the subnational units. The relationship between the central government and subnational units is largely hierarchical, with the central government having the power to delegate or withdraw power from the subnational units.

In a federal government, power is divided between the central government and subnational units, such as states or provinces. Both the central government and subnational units have their own areas of authority and make decisions independently within those areas. The relationship between the central government and subnational units is based on principles of shared power and cooperation.

Option 1, the relationship between legislature and executive, is not the basis of classification of governments as unitary and federal. Option 2, the relationship between executive and judiciary, is also not the basis of classification. Option 4, the relationship between the legislature, executive, and judicial wings of government, is not directly related to the classification of governments as unitary and federal.