The correct answer is:
B) political corruption.
Muckrakers were reformist American journalists who denounced corrupt institutions and leaders and played a highly visible role during the Progressive Era period (1890s-1920s).
Muckraking magazines took on corporate monopolies and political machines while trying to raise public awareness and anger at urban poverty, unsafe working conditions, prostitution, cattle processing, and meat packing; patent medicines, and child labor.
As a result of their efforts, child labor laws were rewritten, food and medicine were protected for consumers and rules for fair business practices were established.