A model that allows for successful change by requiring unfreezing of the status quo (equilibrium state), changing to a new state, and refreezing the new change to make it permanent is known as:

Lewin's Change Management Model

Explanation:

Kurt Lewin in 1940s, came up with his management model known as Lewin's Change Management Model. It involves three step process of Unfreeze, Change and Refreeze.

This first stage is to break down the existing status quo in the Unfreeze stage to realize that the next step, Change is necessary. The employees successfully adapt to the changes. The model then follows Refreeze, which means the employees embark to work with new methods.  

imperial crisis leads to civil war.

roman forces withdraw from britain as goths attack rome.

odoacer topples romulus augustus

huns attack the empire and drive german peoples ahead of them.

the answer your looking for is c. : )