Answer:
D
Explanation:
Population of North America: 579 million
Population of South America: 422.5 million
Combined = 1.1 billion
Differences between Indus, Nile, and Yellow river valley civilizations are (please refer the attached image)
Learn more about the Indus, Nile, and Yellow valley civilizations here:
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D. Puerto Rico.
Puerto Rico, while not a US state, is a US territory.
Digging and chopping similar to the pickaxe.