Answer:
a. United Mine Workers
Step-by-step explanation:
With the background of the threat of First Red Scare and Steel Strike of 1919, United Mine Workers of America under the leadership of John L. Lewis started a strike on 1 November 1919 to demand high wages and low working hours. the impact of the strike can be imagined from the fact that President Wilson had to interfere and workers got 27 percent wage spike but no progress on working hours.