Final answer:
In the Gilded Age, the monopoly control over industries often resulted in lower wages for workers, as monopolies had little competitive pressure to either increase wages or improve working conditions.
Step-by-step explanation:
During the Gilded Age, when an industry was monopolized by one company or trust, workers' wages often suffered. The correct answer to the student's question is B: Workers often earned less because the monopoly controlled wages. Monopolies had significant control over the market, including the labor market, which allowed them to set wages without much competition. Furthermore, the lack of legal restrictions on exploiting employees led to long hours, dehumanizing conditions, and poor pay.
Since monopolies could control almost all aspects of the industry, including labor costs, they had little incentive to increase wages. The dominance of monopolies over their respective industries also meant that there was little competitive pressure to treat workers better or pay them more.
During this era, the theory of bilateral monopoly would suggest that when union membership declined, the equilibrium level of wages would tend to decrease since workers had less power to negotiate for higher wages. It is important to note that despite technological advances and increases in overall prosperity during periods such as the 1920s, gains for workers were often limited due to reduced union power, an influx of immigrants willing to accept poor working conditions, and a societal shift away from organized labor.