To what extent was President Truman Justified in dropping the atomic bomb on the Japanese city of Hiroshima?

To what extent was President Truman Justified in dropping the atomic bomb on the Japanese city of Hiroshima?

U.S. reasons for using the atomic bomb on Hiroshima:
-retribution for Pearl Harbor
-intimidation of the Soviet Union
-testing full effects of the bomb
-ending World War II in Asia
-justifying the expenses of the Manhattan Project
see materials: I aim for 7-8 therefore I need to:
Student has
-explained the five arguments in detail;
-with supporting evidence extracted from sources provided
-and has analysed that one of the reasons was more justified than the others (for example, through ranking / weighing advantages and disadvantages / comparing costs and benefits)
as well as show my critical thinking by: see Criterion D Thinking Critically