Increase of nationalism and capitalism and militarism increased competition
D. Tenochtitlan
Tenochtitlan was the capital of the Aztec nation, and was known for it's splendor, wealth, power, and even size. In fact, Spanish explorers often marveled at the city, and could not believe that the natives were able to create such an empire.
d. corn
It really depends on which Native American tribe is being talked about in the question, but many Native Americans survive on corn, which should then be your answer.
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1861 Creation of the Confederate States of America
This one is true arson is on purpose