According to the Text,why Did Labor Unions Develop

According to the text,why did labor unions develop?

A) to ensure that business owners could control unruly workers
B) to provide a pool of unskilled labor that business owners could draw on in times of economic depression
C) to redress the imbalance of power between workers and employers
D) to force politicians to invest heavily in certain strategic sectors
E) to reduce the alienation of shareholders in large corporations