What sort of monopoly did john rockefeller mostly have?

in 1870, he established standard oil, which by the early 1880s controlled some 90 percent of u.s. refineries and pipelines. critics accused rockefeller of engaging in unethical practices, such as predatory pricing and colluding with railroads to eliminate his competitors, in order to gain a monopoly in the industry. if this , a brainliest would be appreciated!

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