Why did earlier historians consider the Medieval Period the Dark Ages

Answer

The time had no electricity and so it was an age that was quite dark. The era seemed less important than the Renaissance and the Roman Empire. Castles were very dark and did not let in much light.

Explanation:

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.