Answer: C. the creation of the interstate highway system
Step-by-step explanation:
The Interstate Highway system has been lauded as one of the greatest infrastructural additions to the U.S. by the government and it had a profound impact on the economy when it was built after the second world war.
With the Interstate system, places around the United States became more accessible and transportation of goods, services and people became faster and cheaper. This led to more goods and services being produced to feed demand and more producers having access to markets around the United States.