The answer is A.
A- they believe that it was the quickest way to end the war and save American lives
B-that’s malicious, and most people weren’t thinking about that, they wanted to end the conflict now.
C-no, they were informed for what the atomic bomb would do
D-No, they believed that they would win, but using the atomic bomb would save the most American lives.
So the answer is A, I hope this helps!