Question

How was Rockefeller able to build his monopoly across the oil industry?
He bought up oil refineries, cut costs, and reinvested his profits in other refineries.
He confined his business to Ohio so he could buy all the refineries there.
He found newer and cheaper ways to refine oil, increasing his profits.
He began to sell kerosene as well as oil, expanding his market.

Answer 1

He bought up oil refineries, cut costs, and reinvested his profits in other refineries.

Explanation: Rockefeller used aggressive horizontal consolidation (buying competitors), achieved economies of scale and lower costs (better refining methods, tighter operations, railroad rebates), and plowed profits into buying more refineries and related businesses. He also used trusts and vertical integration to control distribution—but he did not confine himself to Ohio, and merely selling kerosene was not the main reason he built a monopoly.