The correct answer is - A. Thought that it would lead to fewer deaths than a land invasion.
Truman decided to order the dropping of the atomic bombs on Japan because he thought that the US army would suffer a lot of casualties if they tried a land invasion. Considering how hard and slow the island to island war with Japan, and how much soldiers were dying, Truman decided to end the war as quick as possible, and as efficient as possible. He ordered the dropping of the atomic bombs, and it managed to have the effect he wanted. Japan surrendered immediately after that, the war was over, and lot of US soldiers' lives were saved. On the other hand, it was a huge humanitarian catastrophe, as hundreds of thousands of innocent people died or suffered badly because of the atomic bombs. The negative effects continued in the decades that came, and are still present today.