Answer: The constitutional/federal amendment process must be proposed by Congress/2/3 majority vote from the House Of Representatives, or by 2/3 of state legislatures.
Not that big on world stuff, but I believe it's because of the cheap wages, since you can pay a lot less to people in China, then say the US.
The answer to this question is 4. Industrialization caused urbanization and a population boom.
I believe the answer you are looking for is: "a violent or destructive protest." The government would be most likely to become involved in a union protest that is violent or destructive.