(mc) which of these technologies was able to spread because of the growth of american railroad networks

The technology that was able to spread because of the growth of American railroad networks was the internal combustion engine. This is a heat engine that generates the combustion process in a chamber. The internal combustion engine makes cars, vehicles, and buses work

Explanation:

the answer to fill in the blank in this question would be the word resource, it is defined as the money, material or people (since human resource is a very valuable good) that a company or a person has at disposition (meaning they can use the resource as they see fit), to be able to complete a task or achieve a goal.  

i think the answer is a and i hope this ; ))