The statement that best shows the power of a unitary government is:
States can establish rules that cities have to follow.
In a unitary government system, the central government holds the primary authority, and any administrative divisions (like states or provinces) derive their power from the central government. This implies that the central government can grant powers to local governments but can also revoke them. Therefore, in a unitary system, the relationship is one where the central government can dictate rules and regulations that localities must follow. The other statements suggest characteristics more aligned with federal systems of government.