Answer:
Correct answer is It was a rapid transition marked by violent internal conflict.
Step-by-step explanation:
Last option is correct as after the death of Julius Caesar a second triumvirate was established. But it didn't last for a long period as civil war broke out.
Octavian fought against Mark Anthony and managed to defeat him after a couple of years of war. After that Augustus was proclaimed as a first Roman emperor.
All options which are saying that it fast peaceful transition are false, as it was a period of civil wars, while I wouldn't say that it was a slow transition as the conflicts didn't last for too long.