What key factor distinguishes a unitary system from a federation?

A unitary system is distinguished by the central government's primary authority over political decisions and administrative functions. In such a system, the central government retains the power to create or abolish local governments and can dictate their powers and responsibilities. This centralization of authority allows for uniform policies and laws to be implemented across the entire nation, ensuring consistency in governance.

In contrast, a federation divides powers between a central government and various regional governments, allowing both to operate independently in certain areas. This means local governments in a federation typically have constitutionally guaranteed rights and responsibilities that the central government cannot encroach upon. Therefore, the correct choice highlights the central government's paramount authority in a unitary system, whereas the other options address attributes that are either characteristic of local governance in a federal system or do not accurately describe the fundamental nature of a unitary system.