Which of the following phrases in the Source 2 most directly challenges the interpretation of events in Western Eurasia c. 100 - c. 500 CE presented in Source 1?

a) "...emphasizing the arrival of named peoples at their assigned places across the map of Europe..."
b) "In this view, movement and arrival were the events of key historical importance."
c) "...the barbarians on their doorstep: Germanic, largely, in the first half of the millenium, then Slavic, largely, in the second..."
d) "...these interactions, not acts of migration, ... were ultimately responsible for generating the new social, economic, and political structures..."