D) Increased immigration in industrial areas.
By 1890, production by factories in American had grown eight times larger than what it had been before 1860. A large part of the workforce came from immigrants coming to the United States and settling in cities, looking for jobs. Ireland was one example of a country from which many immigrants came, looking for work in America, after the devastation of famine in Ireland (especially from potato crop failures).
The Articles required unanimous consent to any amendment, so all 13 states would need to agree on a change. Given the rivalries between the states, that rule made the Articles impossible to adapt after the war ended with Britain in 1783.
PROTECTORATES. The political system that the European countries set up that caused conflicts in the Middle East, is the protectorates political system.