Answer:
The correct answer is B. American Federation of Labor (AFL).
Step-by-step explanation:
The National Labor Union (NLU) was one of the earliest labor federations in the United States, founded in 1866. While the NLU was able to secure some victories for its members, it was short-lived and ultimately dissolved in 1873.
The Knights of Labor (KOL) was a later labor organization founded in 1869. The KOL was more radical in its approach than the NLU, advocating for the overthrow of capitalism and the establishment of worker cooperatives. While the KOL was able to gain a large following at its peak, it ultimately declined due to internal divisions and the organization's involvement in the failed Haymarket Riot of 1886.
The American Railway Union (ARU) was founded in 1893 and was led by Eugene V. Debs. The ARU achieved some notable successes in its early years, including a successful strike against the Great Northern Railway in 1894. However, the organization's involvement in the Pullman Strike of 1894 led to its downfall, as the federal government intervened and sent troops to break the strike.
The American Federation of Labor (AFL) was founded in 1886 and was led by Samuel Gompers. The AFL focused on organizing skilled workers into trade unions and advocated for better pay and working conditions for its members. The AFL was able to secure significant victories for its members, including the eight-hour workday and collective bargaining rights.
Therefore, the most successful union in getting better pay and shorter hours for its skilled members was the American Federation of Labor (AFL).