Reforms moved the economy to one in which government regulations prevent abuses of economic power

This is a progressive reform. A movement for reform that happened approximately between 1900 and 1920. Progressive Reforms were encouraged by the political philosophy of Progressivism and the effect and effort of reformists called Progressives who are comprised of protestors, experts and social critics. Progressives normally held that reckless actions by the rich were mortifying both public and private life. 

d is the answer. leo should include the source.