Over the course of U

Over the course of U.S. history, the federal system has become increasingly "nationalized" in the sense that the federal government's authority has expanded relative to the power of the states. Which factor has been least important in this development?
1-Increased levels of industrialization and urbanization have made the American economy and people increasingly interdependent, requiring national solutions to policy problems.
2-Supreme Court rulings that have broadly interpreted the federal government's constitutional powers.
3-
The states' desire to cede authority to the national government to relieve themselves of some of their policy responsibilities.
4-
The use of federal grants-in-aid as a means of exerting federal authority in policy areas traditionally reserved for the states.