The factor that most contributed to the development of the manor system in Western Europe after the fall of the Roman Empire is:
D. lack of a central authority and infrastructure.
After the fall of the Roman Empire, Europe experienced significant political fragmentation and instability. The absence of a strong central government led to the need for self-sufficient communities, which the manor system provided. Manors became the basic unit of agricultural production and governance, allowing local lords to manage lands, protect their inhabitants, and provide some level of order in a chaotic environment. Other factors, such as agricultural advancements and the influence of the Church, also played roles but were secondary to the overarching need for localized governance and self-sufficiency during this period.