Final answer:
Option (c), Unlike Carnegie, Rockefeller first created a trust to control his oil industry interests, leading to increased market dominance and eventual anti-trust challenges.
Step-by-step explanation:
Unlike Carnegie, Rockefeller first created a trust in which he and his partners combined their oil industries. The trust was a business organization that allowed Rockefeller to gain control over numerous oil companies by having a small group of trustees hold legal ownership. This was done to benefit the investors of Standard Oil, and it was a way to circumvent legal restrictions on forming a monopoly directly. This arrangement enabled Rockefeller to dominate the oil industry, minimize competition, and greatly influence prices.
By employing such a strategy, Rockefeller's Standard Oil Trust at one point controlled a staggering 90% of the nation's oil refineries. While this was not initially illegal, it did raise large anti-trust concerns, resulting in the eventual dissolution of the trust. Rockefeller then turned to a holding company model to maintain his influence and control in the industry.