What Was the Official Reason for Dropping Atomic Bombs on Japan

What was the official reason for dropping atomic bombs on Japan?

A) To punish Japan for Pearl Harbor
B) To test out the new weapon to see how powerful it was
C) To offset a shortage of conventional explosive materials in the United States
D) To save the hundreds of thousands of American lives it was calculated that a U.S.-led invasion of Japan would cost
E) To force the Japanese emperor to give up his claims to divinity and to abdicate