Which of the following did Truman consider as an alternative to dropping the atomic bomb on Japan?

In mid-July, President Harry S Truman was notified of the successful test of the atomic bomb, what he called "the most terrible bomb in the history of the world." Thousands of hours of research and development as well as billions of dollars had contributed to its production. This was no theoretical research project. It was created to destroy and kill on a massive scale. As president, it was Harry Truman’s decision if the weapon would be used with the goal to end the war. "It is an awful responsibility that has come to us," the president wrote.