Final answer:
Labor shortages during WW1 allowed workers to demand better wages and working conditions, strengthening unions in the US.
Step-by-step explanation:
The correct answer is a. Because labor was scarce, workers were able to demand better wages and working conditions. During World War 1, labor shortages occurred in the United States, as many workers were drafted into the military. This scarcity of labor gave workers more bargaining power, allowing them to demand improved working conditions and higher wages. The increased demand for workers also led to the expansion of unions and the recruitment of more members.
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