The Stock Market Crash of 1929 was one of the biggest financial disasters in United States history. This caused thousands of Americans to lose their life savings. Right after this happened, several thousand banks closed due to a lack of currency (paper money). People losing their life savings, banks closing, and banks running out of paper were all short-term effects.
In the long run, banks became more wise about the loans they gave out to individual citizens, making B the correct answer.