Answer: C
. They advocated for the rights of workers in a market economy.
Step-by-step explanation:
American workers were not always protected and were prone to be mistreated and abused in the 19th century. This century saw the United States embracing the Marketing economy such that firms were all about making the most profit they could and they did this at the expense of labor that could be easily replaced if they offered opposition.
To combat this, Labor Unions were formed. These Unions attracted thousands of people due to their strikes successfully forcing companies to treat their employees better in a Market economy that did not care much for the rights of workers.