I do not understand this can someone help.

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

List a few examples of city-states that practiced oligarchy in ancient greece

There are no written records of the first migration of humans to the americas? true or false