The correct answer is:
c. It was involved in a number of violent strikes.
In the late nineteenth century, the American labor movement indeed faced significant challenges, including violent confrontations during strikes, such as the Haymarket Affair and the Pullman Strike. While some labor unions did achieve improvements for workers, they were not universally successful, and they faced substantial resistance from employers and government. The other options do not accurately reflect the realities of the labor movement during that time.