Which of the following statements BEST explains a cause of the Great Depression?
A
Banks failed at a record pace in the 1920s and 1930s because they loaned too much money to outlaw groups such as the Mafia.

B
The stock exchange became more and more careless with its speculation, gambling on casinos and other questionable investments during the 1920s.

C
After the end of World War I, America loaned too much money to failing European countries, many of which could not get their economies back on track and had to default on loans.

D
Overproduction by the American economy caused a surplus supply of goods, creating a cycle of products unsold and people unpaid, banks unable to collect money from loans, and banks failing.