Many Americans were exposed to the ideas of the federalists by the "Federalist Papers".
The gradual decline of the Roman Empire ushered in an era of European history called the Middle Ages, or the medieval period
They created a democracy untainted by wealth, privileged birth or corruption where every (eligible) citizen can take part in politics/ assembly.
I'm gonna go with A & B " It provided a way for people to move west more easily." and "It created a mode for the transport of goods and services to the west." C is also somewhat applicable but I'm not 100% sure about C. Hope this helps.
