Assuming this was the same post made before, this poster is pushing Americans to avenge the bombing of Pearl Harbor by the Japanese by committing to the war effort.
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.
Socialism is a range of economic and social systems.
