The correct answer is C) 90.
Ninety percent of the nation's oil business is controlled by the Standard Oil Company.
John D. Rockefeller (1839-1837) was the was the owner od the Standard Oil Company. He built the oil empire in America becoming in a monopoly that controlled 90% of pipelines and refineries by 1880. His oil empire was the target of many critics because he was accused of controlling the industry and eliminating the competition. The US Supreme Court decided in 1911 that the Standard Oil Company had violated anti-trust laws and ordered to dissolve the monopoly.
The other options of the question were A) 50, B) 75, and D) 100.