1) Contextualization: Which event brought on the Great Depression and marked the end of the prosperity of the 1920's?

stock market crash

Explanation:

The financial exchange collapse of 1929 signaled an end to the boom of the 1920s. The stock market collapse signaled the onset of a era of economic tough times known as the Great Depression that continued into the 1930s.Cash transactions are substantially rising and also impacts the banks. So we may conclude that overproduction, so many credit transactions, asset inflation, and bank defaults at the end of the 1920s better summarize American economic problems

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i believe the correct answer is option b. most eastern european nations joined nato.

though i could be wrong, option d. the eastern european nations were granted complete independence, would be another choice.

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i believe the answer to your question is b. pay your bills early