The correct answer is B.
The development of cheap iron in the US was the major factor that lead to the building of skyscrapers. Being able to produce iron cheaply can be contributed to Andrew Carnegie. This American business mogul perfected the Bessemer process in several factories across the eastern part of the US. From there, he was able to sell cheap iron to American businesses for the purpose of growing their empire.
The answer is D. Because Communism is the polar opposite of what America is built on.
The answer is B!!!!
Just answer that question
Shang rulers expanded their kingdom by land purchases which expanded their borders.
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