Final answer:
The Standard Oil Company was found to have violated the Sherman Antitrust Act, leading to its breakup by the U.S. Supreme Court in 1911.
Step-by-step explanation:
The court determined that Standard Oil had engaged in unreasonable business practices that were in violation of the Sherman Antitrust Act, which is option (A). The Sherman Antitrust Act, passed in 1890, was the nation's first antitrust law and aimed to limit the power of trusts—large business entities that controlled a significant portion of a market or industry. The U.S. Supreme Court in 1911 famously used the Sherman Antitrust Act to uphold the government's decision to break up Standard Oil, which had controlled about 90% of the country's oil refining. Standard Oil was split into 34 independent companies, including well-known corporations like Exxon, Mobil, Amoco, and Chevron.