<span>There were several reasons for the fall of the Roman Empire. Each one intertweaved with the other. Many even blame the initiation of Christianity for the decline. Christianity made many Roman citizens into pacifists, making it more difficult to defend against the barbarian attackers.</span>
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.
