Final answer:
D. The 'supremacy clause' in Article VI, Clause 2 of the Constitution establishes that the Constitution, national laws, and treaties are the supreme law of the land, taking precedence over state laws.
Step-by-step explanation:
The constitutional clause that affirms that national laws and treaties, made under the authority of the Constitution, are the supreme law of the land is D. the supremacy clause. This clause, specifically integrated into Article VI, Clause 2 of the Constitution, ensures that federal law takes precedence over state laws and constitutions. In practice, if there is a conflict between federal and state laws, the laws of the national government, as long as they are consistent with the Constitution, are to be followed. This principle establishes a clear hierarchy of laws, with the Constitution at the top as the supreme law of the land, followed by national laws and treaties.
It's important to note that the powers not delegated to the national government are reserved to the states, which is clearly indicated by the Tenth Amendment, reinforcing the structured balance of power between the federal and state governments within the United States.