The correct answer is D) The United States, which prior to the war provided most global manufactured and agricultural goods, fell into an economic depression which caused a global depression.
What was NOT a serious economic problem undermining the world economic stability after World War I was "The United States, which prior to the war provided most global manufactured and agricultural goods, fell into an economic depression which caused a global depression."
Indeed, what happened in the United States after World War 1, was a period of economic prosperity called "the Roaring 1920s," in which the US citizens had money to buy things like cars, houses, or furniture. Most of the purchases were on credit. The "dream" ended until 1928. One year later, on October 29, 1929, the US stock market crashed, provoking the Great Depression. Thousands of Americans became jobless, companies closed as well as banks.