The correct answer is: "investigative journalism".
Ida Tarbell was one of the leading muckrakers in the Progressive Era (late 19th and early 20th century) . In 1904 she published her most famous book; The History of the Standard Oil Company.
The term muckracker was used to describe a generation of journalists who aimed the reformation of corrupt institutions and leaders during the Progressive Era. Nowadays this term has been actually substituted by the expression "investigative journalism".
