91 POINTS PLEASE HELP
Read a paragraph from an essay supporting Truman’s decision to use the atomic bomb against Japan during World War II.

[1] Many people have argued that nothing could justify the president’s use of the atomic bomb because it killed so many innocent civilians. [2] Truman himself refused to drop a third atomic bomb on Japan because he was horrified by the death and devastation it had caused. [3] However, he never regretted his decision to use it in the first place. [4] Using the bomb brought an immediate end to a war that might have gone on for months or even years longer. [5] It is impossible to put a number on how many more deaths the continuing war might have caused, but there are indications. [6] Millions had already died in the Pacific theater. [7] Whenever US troops invaded an island, they knew the fight was to the death. [8] In the battle for Okinawa alone, there had been almost 50,000 US casualties, while Japan had suffered some 90,000 military deaths and at least 100,000 civilian deaths. [9] With his decision, Truman put an end to the slaughter.

Which of these sentences should be followed by a citation?
sentence 2
sentence 4
sentence 5
sentence 9