The response that best demonstrates how biased views on race and reliance on the writings of the wealthy elite led to mistakes in early twentieth-century textbooks about American history in the Civil War era is: that enslaved people were happy under slavery.
This statement reflects a biased and skewed perspective often propagated by those in power, particularly from the wealthier classes who benefited from slavery and sought to portray it in a more favorable light. Such views minimize the brutal realities of slavery and contradict the experiences and resistance of the enslaved people themselves.