Answer:
E. The flow of immigrants into the country increased dramatically in the last two decades of the 19th century.
Step-by-step explanation:
One of the reasons why unions were not more powerful in the latter half of the nineteenth century was because the flow of immigrants into the country increased dramatically. This meant that workers had little bargaining power as they could easily be replaced. Moreover, people who had recently arrived to the country were less likely to be involved in politics and participate in unions, due to economic necessity or language and cultural barriers.