Final answer:
Henry Adams's former master attempted to gain advantage over former slaves by exploiting their labor and withholding wages, maintaining control and subjugation even after slavery ended.
Step-by-step explanation:
Henry Adams's former master tried to take advantage of his former slaves primarily by exploiting their labor and withholding wages, which aligns with Option 3: By exploiting their labor and withholding wages. In the aftermath of slavery, Black codes and other measures were used to tie formerly enslaved people to the land, forcing them to sign contracts with their former masters that restricted their employment opportunities and prevented them from influencing wages and working conditions. This coercive system maintained a form of dependency and control over former slaves, akin to the restrictions they endured during enslavement. These practices were ultimately part of a broader effort to subvert the newly gained freedoms of African Americans and reinstate systems of racial subordination and economic exploitation after the Civil War.