What does the Constitution primarily establish?

The Constitution primarily establishes the framework for government and delineates the powers and responsibilities of its various branches. It sets up an effective system of governance that delineates the roles of the legislative, executive, and judicial branches, ensuring a balance of power through checks and balances. This structure is essential for maintaining the rule of law and protecting individual rights.

Option A, which suggests limits on government spending, is a specific aspect of governmental control and accountability that can be found in certain fiscal policies and amendments but does not encompass the overarching purpose of the Constitution.

Option C mentions controlling state laws, which is partially addressed by the Constitution through the Supremacy Clause, ensuring federal law takes precedence over state law. However, this is not the primary focus of the Constitution's establishment.

Option D involves regulating foreign trade, which is one of many powers granted to the federal government through the Constitution, but this is again just one function within a broader framework.

Thus, the answer that best captures the essence of the Constitution's role is that it sets up the government and defines its powers, establishing the foundational principles upon which the United States operates.