What was a key feature of the manorial system in medieval Europe?

The correct answer highlights the manorial system's economic self-sufficiency and its dual role in providing defense. During the medieval period, especially in the context of feudalism, the manorial system structured rural economies around the estate (or manor) of a lord. Each manor was largely self-sufficient, meaning that it produced most of the goods and services its residents needed to sustain themselves. The peasants or serfs working the land cultivated crops, raised livestock, and engaged in various trades necessary for daily life.

Additionally, manors were often fortified or strategically located to offer some protection against external threats, such as invasions or raids. Thus, the arrangement not only facilitated agricultural production but also ensured a level of security for those living and working within the manor's confines. This self-sufficiency and defensive capability were critical for survival in an era characterized by instability and a lack of centralized governance.

The other options, such as large bureaucratic governance, centralized political power, and the development of international trade, do not accurately represent the essence of the manorial system, as it was largely localized and focused on self-reliance rather than broader governmental or trade networks.