The So-Called Barbarian Invasions of the Roman Empire in the Late

The so-called barbarian invasions of the Roman Empire in the late fourth and fifth centuries CE were, in actuality, what?

A) a consolidation of power among non-Roman tribes under kings who could coordinate widespread attacks against Roman troops
B) an armed insurrection against Christian missionaries who tried to force the conversion of pagan peoples to Christianity
C) a more violent and chaotic form of immigration pouring into the empire
D) a massive slave revolt in the provinces that destroyed the empire