What three explanations have been given for the collapse of the mayan civilization

Maya historians have generally settled on a combination of three main factors which could have caused the Maya collapse: warfare between city-states, overpopulation, and drought. The factors were not always contemporary or found all together in a single city.

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.