Why did medieval manors have to be self suffcient

A manor was the Lord's estate. Manors had to be self sufficient because of how dangerous it was to leave them. One way manors were self sufficient is that they had plenty of farms to grow crops. ... The manor was also self-sufficient because it provided small houses for the serfs.

Explanation:

whats the question? im not quite understanding your question.

the graph shows the spread of railways in the 1800s.

based on the graph, the conclusion that can be drawn about germany is answer d)   by 1880, germany had more rail lines than great britain and russia.