Final answer:
The term 'independent' best identifies the power relationship between government layers under dual federalism, where federal and state governments operate within their own realms without interference.
Step-by-step explanation:
The power relationship between the layers of government under a system of dual federalism is best identified as independent. In contrast to cooperative federalism, where the federal and state governments work together to solve national problems, dual federalism is characterized by clear and distinct separation of powers. Both the federal and the state governments operate within their own realms of jurisdiction, without interference from the other.
This form of federalism is likened to a layer cake where each layer has its own distinct and separate area of responsibility and authority. The concept of concurrent powers does not typically play a significant role in dual federalism, in contrast with later periods of cooperative and competitive federalism where the layers of government take on more overlapping responsibilities.