What are three ways carnegie, rockefeller and other corporate leaders consolidated control over their industries?

The ways that Carnegie, Rockefeller and other corporate leaders consolidated control over their industries is that they established a monopoly or trust, which centralized control of a number of oil-related companies under one board of trustees. As a result, they owned nearly the entire oil business in the United States, and could set prices at will. Companies in other industries quickly imitated their trust model and used their broad market control to push prices higher.