Final answer:
The invention that led to an increase in the demand for slaves was the cotton gin.
Step-by-step explanation:
C. The cotton gin
The invention of the cotton gin by Eli Whitney in 1793 greatly increased the demand for slaves in the Southern United States. The cotton gin made it easier and more efficient to separate the seeds from the cotton fibers, leading to a significant expansion of cotton production. This increase in cotton production created a higher demand for slave labor to cultivate and pick cotton crops.
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