What were the limitations and the achievements of urban governments run by ethnic political machines?

During the cold war, which of the following groups of countries would have all been"behind the iron curtain"

Which of the following is an example of the pull factor known as economic migration? a. better educational opportunities pulling people towards a new country b. mexican laborers entering the us to work in agricultural jobs c. joining family members that are already in a new country d. crop failures driving people away from their country i am unsure on this question, i was thinking b? but i could be wrong.

What was the overall impact of eli whitneys introduction of interchangeable parts?