Answer:
The Allies decided on that strategy because they:
B. Believed that Germany posed a more serious threat than Japan did.
Explanation:
In World War II, the Allies were Great Britain, France, the Soviet Union, the United States, and China. These were the powers that opposed the Axis (Germany, Italy, and Japan). The reason why the Allies decided on a "Europe First" strategy was because of the threat Nazi Germany represented. As we know, under Hitler's control, Germany was a force to be reckoned with. The Allies saw less urgency in dealing with Japan, since Germany was a more destructive war machine.