Which is a reason for the rapid growth of labor unions in the late 1800s

A. the low wages paid to factory workers

Explanation:

The life of a nineteenth-century American industrial worker was difficult. Even in good times, wages were low, the journey of work was long and they had to work under hazardous conditions. Little of the wealth generated by the nation's growth went to its workers. Besides, women and children constituted a high percentage of the workforce in some industries and often received only a fraction of the salary that men could earn.

The first major effort to organize groups of workers at a national scale came up with the Noble Order of the Knights of Labor in 1869. Initially as a ritualistic and secret society, organized by Philadelphia Confections workers in Philadelphia Confections and advocating for a cooperative program, it was open to all workers, including African Americans, women, and farmers. The Order slowly grew until the railway workers gained a strike against Jay Gould, the great Railways baron in 1885. In one year they conquered another 500,000 affiliated workers, but because they are not in harmony with pragmatic unionism and are unable to repeat this successful, the Knights of Labor soon declined.

while it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton.

explanation:

before eli whitney's invention of the cotton gin, picking and cleaning cotton was a slow, labor-intensive job. workers, usually slaves, had to pick the seeds from the cotton fibers by hand. this invention made it possible to grow large amounts of cotton on big farms and make money.