Final answer:
Muckrakers influenced Progressive political reform by exposing societal problems and pushing for legislation such as the Pure Food and Drug Act and the Meat Inspection Act of 1906, with examples including Upton Sinclair's 'The Jungle' prompting food safety regulations.
Step-by-step explanation:
The statement that best explains how muckrakers influenced Progressive political reform is that muckrakers influenced the passage of the Pure Food and Drug Act and the Meat Inspection Act of 1906. Muckrakers were journalists who exposed problems in American society, such as corrupt machine politics, poor working conditions in factories, and unacceptable living conditions for the working class. Their investigative journalism played a critical role in the Progressive Era by raising public awareness and putting pressure on legislators to implement reforms. For instance, Upton Sinclair's novel 'The Jungle' vividly detailed the horrendous conditions in the meatpacking industry, leading President Theodore Roosevelt to push through legislation that greatly improved food safety standards. Consequently, the Pure Food and Drug Act and the Meat Inspection Act were passed, establishing federal oversight of food safety and labelling requirements.