The correct answer is they introduced new business practices that created large industries and produced great wealth for a few.
Monopolies and trusts were devloped by different individuals like John D. Rockefeller, Andrew Carneige, and JP Morgan. These individuals used different business practices to accumulate massive wealth.
For example, many of these trusts used horizontal integration. This strategy resulted in buying out their competitiors within their market to ensure that there was limited competition.
Along with this, vertical integration was used. This resulted in trusts buying companies to control all of the means of production for their product. This includes railroads, factories, etc.
