The correct answer is: "Trade slowed down".
The Ancient era in Europe, characterized by the power and great expansion of the Roman Empire, was a time of economic expansion. Mediterranean powers established very profitable international trade relationships among themselves.
On the contrary, with the dismantling of the Western Roman Empire in 476 (the end of the Ancient Era), many small and less developed tribes controlled the European territories. They evolved to feudal socities, that became separated autarkies, with very few trade among them, replacing the very intense trade relationships that were the norm during the Ancient Era.