Final answer:
The Ku Klux Klan reappeared in the 1920s due to the racist culture post-World War I, nativism, and white supremacy, along with mainstream society's shared racial superiority beliefs.
Explanation:
The conditions that allowed the Ku Klux Klan to reappear in the 1920s were:
- World War I and its aftermath created a widespread racist culture, fostering nativism and white supremacy.
- Nativism and white supremacy were on the rise in the United States during this period.
- Mainstream society shared basic assumptions of racial superiority and intolerance for immigrants, contributing to the Klan's growth.
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