Progressive Era (1890–1920), was a period of dramatic political reform and social activism. Progressive reformers denounced corruption and incompetence in government and used government power to regulate businesses and workplaces through regular on-site inspections, regulatory commissions, and antitrust laws.
In other words, the worst excesses and abuses of urban-industrial development corporate monopolies, child labor, political corruption, hazardous working conditions, urban ghettos were finally addressed in a comprehensive way.
Which gives us the right answer letter D. they represented forward thinking about political changes.