Final answer:
Muckraking journalists exposed social, economic, political, and cultural challenges such as child labor, corruption, unsafe working conditions, and monopolistic business practices, thereby advancing Progressive Era reforms.
Step-by-step explanation:
Muckraking journalists focused on exposing a variety of issues that were prevalent during the early 20th century, often associated with the adverse effects of industrialization. Muckrakers delved into social, economic, political, and cultural challenges facing American society. They uncovered problems such as child labor, corruption in government, unsafe working conditions, and unethical business practices of monopolies, which spurred the Progressive Era reforms including laws such as the Pure Food and Drug Act of 1906.
Through their diligent investigative reporting in publications like McClure's and serialized novels such as Upton Sinclair's 'The Jungle,' they brought to light the darker aspects of society and influenced legislation aimed at remedying these issues. President Theodore Roosevelt famously dubbed these journalists as "muckrakers," a term that acknowledged the filth they raked up through their hard-hitting exposés. Their work informed and energized the public, leading to greater regulatory policies and the establishment of government agencies such as the U.S. Food and Drug Administration (FDA).