The Collapse of the Han and Parthian Empires Differed in Which

The collapse of the Han and Parthian empires differed in which important respect?

A) Centuries of political fragmentation followed the Han collapse, while the Parthian empire was quickly replaced by Sasanid rule.
B) The Han empire fell to ecological disasters, while the Parthians fell to internal strife.
C) The Parthian collapse was followed by decades of political disorientation, while the Han dynasty was immediately replaced by another strong ruler.
D) The Parthians fell to foreign invaders, while the Han only encountered internal enemies.