Answer:
C. They sold their oil refineries to Standard Oil to increase its monopoly.
Step-by-step explanation:
Standard Oil Company was established by John D. Rockefeller in Cleveland, Ohio in 1870.
By 1873 Standard Oil had obtained around 80 percent of the refining limit in Cleveland, which established approximately 33% of the U.S. all out. The securities exchange crash in September of that year set off a retreat that went on for a long time, and Standard Oil rapidly exploited the circumstance to ingest refineries in Pennsylvania's oil area, Pittsburgh, Philadelphia and New York. By 1878 Rockefeller had accomplished control of almost 90 percent of the oil refined in the U.S., and presently he had overseen a large portion of the oil advertising offices in the U.S.
Standard Oil at first centered around flat mix by dealing with other oil refineries. In any case, step by step the combination likewise wound up vertical (i.e., reached out to different phases of generation and circulation), for the most part by getting pipelines, railroad tank autos, terminal offices and barrel producing processing plants.