Final answer:
The authority over slaves is a form of economic necessity.
Step-by-step explanation:
The belief that authority over slaves is a form of political power is not accurate. Slavery in the United States was primarily driven by economic necessity. The Southern states relied on slavery for their agricultural economies, particularly the production of lucrative crops like cotton. Slavery was seen as essential for maintaining the South's economic independence and ensuring its prosperity.
Therefore, option 2: Economic necessity is the correct answer.