Why Did the United States Drop an Atomic Bomb on Hiroshima

Why did the United States drop an atomic bomb on Hiroshima?

A) The invasion of Japan was certain to cost as many as 250,000 American lives.
B) There was no indication that Japan was at all willing to surrender.
C) With the Soviet Union out of the war, the United States was to face the defeat of Japan on its own.
D) Since the United States had spent years and millions of dollars developing the weapon, it was going to use it in the war.
E) Hiroshima was a central site of weapons production in the Japanese empire.