In Early 1945, the United States Was Extremely Eager to Secure

In early 1945, the United States was extremely eager to secure the Soviet Union's participation in the projected invasion of Japan because

A) the Soviets would become so engaged in East Asia that they would not expand further into central Europe.
B) without Soviet help, the Japanese could not be defeated.
C) American casualties were expected to be high if only Americans were involved.
D) Roosevelt believed that Stalin's involvement in Japan could help to control the communists in China.
E) Roosevelt did not want Stalin to become aware of the atomic bomb secret.