Answer:
C. By claiming Iraq had weapons of mass destruction, making it a threat to national security
The 1920s were a unique time in the United States in the sense that it was a time of great economic prosperity and also great social woe. What led to this tension was a mix of rising immigration levels and and irresponsible attitude towards money and spending.
It would be "industrialization," that was a significant factor in both the german wars for unification and United States' Civil War, since Industrialization led to an irreconcilable economic split between two more major segments of each area.