Final answer:
The correct answer is option a. The argument NOT used by Southerners to defend slavery was that the constitution protected slavery south of the Ohio River. Instead, they argued for its benefits, racial justification, and biblical support, while criticizing Northern wage labor.
Step-by-step explanation:
The argument that was NOT used by Southerners in defense of the institution of slavery is d. The constitution protected slavery south of the Ohio River.
Southern defenders of slavery utilized various justifications, such as the existence of slavery in biblical times, the argument that Northern wage workers were treated more inhumanely, and the belief that the curse on Cain justified the enslavement of blacks.
These justifications were part of a broader set of arguments that promoted slavery as a positive good, compared favorably to wage labor in the North, and defended the racial hierarchy and paternalistic nature of slavery.
Indeed, Southern arguments included the idea that slavery was a form of care, where slaves did not have to worry about securing food, clothing, or shelter, provided by their masters.
James Henry Hammond advanced this notion with his mudsill theory, stating that all societies had a lower class that performed menial tasks, and in the South, this role was filled by slaves, which allowed white Southerners to pursue higher societal roles.
Additionally, figures like George Fitzhugh used racial theories to argue that blacks were inferior and benefited from the paternalistic nature of slavery, which they portrayed as more benevolent than wage slavery in the North.