Answer:
The answer to your question is D. Appalachian Mountains
Explanation:
It was known that there was an economic boom taking place just after the second world war. It could be due to effective economic policies implemented by various governments. Such policies include the reduction of the tax rates, and economies were regulated so as to avoid excessive spending.
Answer:
A. that the United States was powerful enough to stop new colonization in the Americas
Explanation:
The Monroe Doctrine basically stated that the US would stay out of European affairs while warning Europe not to interfere in the Americas or else