Okay so, the Great Depression of 1929 was the worst economic downturn. It lasted about 10 years (1929-1939). It caused Wall Street into a panic and wiped out MILLIONS of investors. It also caused troops returning from the war, which created a surge in the civilian labor force and more unemployment. One reason why this happend was because the stock market crash.
C, Charles de Gaulle was not part of the big three. Poor fella kinda got left out lol. Hope this helps :)
They could gain new territory, a possible route to India by ocean or natural resources