Answer:
During the Industrial Revolution, the US underwent a technological advancement and a remake of how the economy worked. One of these technological advancement was the assembly line, which helped speed up production, as well as create "specialized" jobs (jobs in which a worker specializes in a part of the creation, such as creation of the engine and only the engine for a car, for example, in case you are wondering - remove the parenthesis and content inside). These changes in how factories worked helped with the mass exodus of the population from the rural areas to cities for higher pays, which helped with the population boom, and the soon to be restructuring of how cities worked and the services they provided. Without the Industrial Revolution, the US would not be the economically (& later miliatry) giant that she is right now.
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When Cuba and the Soviet Union started to trade nuclear weapons.
Common Sense is the answer
Yes they do lie between both tigris and euphrates mountains
The bourgeoisie, because they were like the middle class, and without them, the social classes would be the same as before.