Answer:
C. fall of the Roman Empire
Step-by-step explanation:
The Western Roman Empire fell in 476 when Goth leader Odoacer deposed the last Western Roman Emperor: Romulus Augustulus.
This event is usually considered the start of the Middle Ages in Western historiography. The reason is that the political, social, and economic landscape in Europe changed dramatically.
The old Empire, which had ruled a large part of the continent for centuries had fallen, and a new continental order was to be formed after that.