The entrance of the United States into World War II was preceded by 3. American aid to help Great Britain defend itself against German aggression. Using policies like "cash and carry" and the Lend-Lease Act, the US was able to provide ships, arms, and supplies with the Allied forces without actually joining the war. Eventually, however, the United States would in fact be drawn to war and send troops overseas to fight the Axis forces.
Most likely A because people where greedy and thirsty for money and connections
"A. The English king made claims to the French throne" is a reasonable answer but it should be noted that the origin of this war is very complex and many people are still guessing.
Many people supported the war by many volunteer efforts. Labor efforts have changed many had to ration over Gasoline, clothes and food to support the men at war. Many of the durable resources such as cars, housing goods, and appliances were banned until the war was over. Many people also have quit their jobs, schools etc to work at industrial centers. Prices and wages were also very controlled. This was also a good time for women to step up and work to take the jobs the men had as well! There is so much more but these are a few of them.
I hope this helped you!