Final answer:
Monopolies engaged in unfair practices such as charging high prices and paying low wages, which many Americans considered exploitative and unjust.
Step-by-step explanation:
Monopolies allowed companies to engage in unfair practices that many Americans considered exploitative. One such practice was the ability for a monopoly to charge high prices for their products, taking advantage of their exclusive control of the market. This meant that they could set prices without fear of competition and potentially exploit consumers. Additionally, monopolies could pay low wages to their workers because they had no competition, which was seen as unfair to the workers. These practices led many Americans to view monopolies as unjust and detrimental to society.