Which development most likely contributed to the conditions described by Riis?
A. Urban factory workers demanded immigration restrictions to
protect their jobs from new immigrants willing to work for lower
wages.
B. The Homestead Act encouraged people to start farms in the West,
and new immigrants fleeing hardship craved their own land.
C. Railroads connected cities and markets from coast to coast,
making it easier for new immigrants to migrate between shifting
employment opportunities.
D. Mechanization shifted urban employment to largely unskilled
labor, and new immigrants provided a ready pool of low-wage
workers.