Final answer:
Elmina was the main slave trading center on the West African coast in the eighteenth century.
Step-by-step explanation:
The main slave trading center on the West African coast in the eighteenth century was b) Elmina. The Portuguese built the castle of St. George of the Mine, later called Elmina, in the fifteenth century. This fortress gave the Portuguese a foothold in the West African gold trade and became one of the earliest direct links between European slavers and the slave markets of the African interior.