Which feature of the Social Security Act of 1935 most directly implemented the federal-state arrangement described for unemployment…

The unemployment system in the Social Security Act used a federal payroll tax with credits for employers contributing to approved state unemployment systems. That gave states an incentive to create programs while preserving federal standards, so D is correct. Choice A is tempting because it sounds national, but states kept substantial responsibility for design and administration, not identical federal benefits. Choice B drops the tax mechanism and approval standards that defined the arrangement. Choice C relies only on state and local taxes, which would lack the federal incentives and safeguards the source describes.