Please help i don’t know the answer :)

Why were the numbering trials held from 1945 to 1946 ?

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.

The original term of was descriptive of lower-class people who performed manual labor.