What did john d. rockefeller do to establish standard oil as a monopoly?

bought stock options.

Explanation:

Standard Oil benefited from the purchase of stock options and became the world's largest oil company. Numerous competitors were absorbed by Standard Oil for the purchase of stock options. As a result, production increased and prices became competitive. The oil industry flourishes and Standard Oil becomes the leader of this new market, becoming a monopoly.

d

explanation:

after the roman empire, the catholic church began to unify by taking on many duties of a government.