Final answer:
The internal slave trade was a system where slaves were bought and sold exclusively within the Southern states.
Step-by-step explanation:
The statement that accurately describes the internal slave trade is option b) It was a system where slaves were bought and sold exclusively within the Southern states. The internal slave trade refers to the legal trade of slaves between states, along rivers, and along the Atlantic coastline in the United States. The trade involved the buying and selling of enslaved individuals within the Southern states and was a major business enterprise in the antebellum South, contributing to the region's economy.