What was the main cause of the Great Depression?

The stock market crash of 1929 and the subsequent economic failures are considered the main cause of the Great Depression due to their immediate and profound impact on the U.S. and global economies. The crash marked the beginning of a severe economic downturn that saw significant declines in consumer spending and investment. As stock prices plummeted, banks failed, businesses collapsed, and unemployment soared, leading to a widespread loss of confidence in economic stability.

Following the crash, a series of structural weaknesses in the economy were revealed, including overproduction in industry and agriculture, bank failures, and a lack of international trade due to protectionist policies. This created a downward spiral where reduced consumer purchasing led to further declines in production, job losses, and more bank collapses, deepening the economic crisis.

While the other options reference significant historical events, they do not encapsulate the primary trigger for the Great Depression. The rise of fascism, World War I reparations, and the agricultural boom all played roles in the broader context of the interwar period but did not directly initiate the widespread economic collapse like the stock market crash did. Thus, the crash serves as a clear catalyst for the onset of the Great Depression, making it the correct answer.