The correct answer is B) advocated a single union for all workers.
During the early twentieth century, the Industrial Workers of the World advocated a single union for all workers.
In the long history of labor unions in the United States, that had fought to defend the rights of workers, the Industrial Workers of the World had an important place and distinguished itself for grouping all kind of workers in what is more formally known as general unionism and industrial unionism. The first one is the union labor that group workers of many industries. The second one, accept unions of just one industry in specific. The wobblies, as people called this Industrial Workers of the World members, founded the union in the city of Chicago, Illinois, in 1905.