How did Standard Oil affect the U. S. economy as a whole during the Second Industrial Revolution?

A. By encouraging competition among small companies
B. By using profits to raise wages for refinery workers
C. By supporting government safety reforms in industry
D. By helping develop the country's infrastructure

D. By helping develop the country's infrastructure

Explanation:

John Rockefeller was a pioneer in horizontal integration in the American oil business. Beginning in 1865, he bought up oil wells, oil pipelines, railways and refineries and, in the end, destroyed almost all of the competitors of his Standard Oil company. By 1879, Rockefeller controlled 90% of US refining. Its pipelines directly connected Pennsylvania oil wells with refineries in New Jersey, Cleveland, Philadelphia, and Baltimore, which significantly reduced the cost of production. Standard Oil was the first trust company to centrally manage Rockefeller oil companies in each state where its refineries and pipelines were located. Trusts have become a common method of monopolizing US production and extracting superprofits from production by inflating prices in the absence of competition. Given the unprecedented scale of the Standard Oil network, the company has developed new methods for managing, financing, and organizing its business.

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"they had a large area of land that they owned."