Question

a pioneer of investigating journalism, this muckraker focused on unfair practices of large corporations. ida tarbell theodore roosevelt upton sinclair robert lafollette

Explanation:

Ida Tarbell was a muckraker known for her investigative journalism on Standard Oil's unfair practices. Theodore Roosevelt was a president, Upton Sinclair focused on the meat - packing industry in "The Jungle", and Robert LaFollette was a Progressive - era politician.

Answer:

A. Ida Tarbell