The Spending of Enormous Sums on the Original Atomic Bomb

The spending of enormous sums on the original atomic bomb project was spurred by the belief that

A) a nuclear weapon was the only way to win the war.
B) the Germans might acquire and use such a weapon first against the Allies.
C) the Japanese were at work on an atomic bomb project of their own.
D) scientists like Albert Einstein might be lost to the war effort.
E) the American public would not tolerate the casualties that would result from a land invasion of Japan.