The correct answer is B) controlled most domestic oil production.
The strategy that John D. Rockefeller used to strengthen Standard Oil was to control most domestic oil production.
In a time where the United States government did not have any type of control to limit the creation of monopolies, John D. Rockefeller was smart enough to make his company grow through the acquisition of mostly all of his competitors. The Standard Oil Company controlled most domestic oil production. He created a monopoly that controlled the extraction, oil production, and distribution systems, to became one of the wealthiest and powerful men of its time.