问题详情

TheUnitedStatesenteredthewaragainstGermany
A.becauseGermanydeclaredwar
B.becauseJapanwasanallyofGermany
C.afterGermanyhadsignedtheNazi-SovietPact
D.afterpeacefuleffortshadfailed
请帮忙给出正确答案和分析，谢谢！