Final answer:
The stock market crash of 1929 triggered the onset of the Great Depression.
Step-by-step explanation:
The correct answer is OC. stock market crash. The onset of the Great Depression in the 1930s was triggered by the stock market crash of 1929, also known as Black Tuesday. This event marked the collapse of the stock market in the United States, leading to a widespread economic downturn.
Learn more about The trigger event for the Great Depression