The correct answer is - D. It was widely agreed that a traditional invasion of Japan would drag the war on for years and lead to may, may more deaths than the atomic bomb.
The US officials decided to use the atomic bombs on Hiroshima and Nagasaki in Japan because of two reasons. The first and more important one was to put an end to the war as quickly and efficiently as possible, minimizing the deaths of their troops as much as possible. The second one was to create an image of a country that reached a level of global military power, in order to boost its global reputation and cause fear at other nations.
Both of those things worked out very fine for the USA. They ended the war with Japan in no time, and they gained a status of a global military powerhouse.
