The correct answer is C) vast trade networks.
The reason that drew tribes to migrate to Europe around 300 was the vast trade networks.
This migration period also receives the name of Barbaric invasion and was the movement of people to European territory from 300 to 700 CE. Tribes like the Vandals, the Huns, Bulgars, and the Goths emigrated to Europe after the fall of the Roman Empire due to the trade networks and new opportunities this region offered.