How did railroad expansion make natural resources more available in the United States?

by increasing the amount of natural resource deposits

by making it possible for natural resources to be transported to different cities and towns

by using natural resources to build tracks and train equipment

by transporting people to cities and towns where they could purchase natural resources

by making it possible for natural resources to be transported to different cities and towns

Explanation:

The railroad expansion was of great importance for lot of things in the United States, including the transportation of people, connectivity between the distant cities and towns, as well as for transportation of natural resources. As with the railroad the natural resources could have been transported quickly over long distances, and plus in very high quantities, it made them much more available. This meant that the natural resources didn't had to be manufactured and used only in the area where they can be found, but instead they can be transported to other places to be manufactured in higher quantities, and thus being sold in a much larger market.

b by making it possible for natural resources to be transported to different cities and towns