What were the main themes of the Progressive Era?

The correct answer focuses on the reforms that characterized the Progressive Era, which spanned from the late 19th century into the early 20th century. This period was marked by a widespread movement aimed at addressing the social, political, and economic challenges that arose from rapid industrialization and urbanization.

Key themes included combating corruption in government and business, promoting social justice, and addressing issues of inequality. Reformers sought to eliminate political machines and corrupt practices, ensure fair labor standards, protect consumers, and promote women's suffrage. Additionally, the Progressive Era highlighted the need for improvements in public health, education, and workers' rights, illustrating a collective desire for a more equitable and just society.

In contrast, the other options reflect themes that are not representative of the Progressive Era’s primary focus. Economic prosperity and overseas expansion align more with periods of imperialism and the resulting US foreign policy approaches. Isolationism and military build-up pertain to different historical contexts, particularly leading up to World War I. Finally, while tradition and the preservation of cultural values are significant in American history, they do not encapsulate the reform-driven ethos that characterized the Progressive movement.