Answer:
C. Increase in available labor source
Explanation:
During industrialization, many new workplaces opened up and many more people were able to work. Beforehand people would usually work at their own farms with their families.
With industrialization and technology development, factories began to open up. Factories were huge as mass production was beginning, and at the time all work had to be done by people and their workforce. This is why there were many vacant workplaces. There was a promise of workplaces in the cities and ideas it might bring more wealth.
People began moving to the cities because of this, looking for jobs. There were also many immigrants coming to the US looking for a better life (for example, people from Ireland running away from famine and hard life).
This meant there was a place to work and people were able to work. There was a huge increase in the labor source.
