The correct statements are:
1. The Manhattan Project in the United States developed the first atomic bomb.
2. The atomic bomb was first tested on July 16, 1945, in a desert in New Mexico.
3. The first time an atomic bomb was used in war was at Hiroshima.
4. The bomb dropped on Nagasaki was more powerful than the one dropped on Hiroshima.
Statements 3 and 6 are incorrect. President Truman, not Roosevelt, made the decision to use the atomic bomb on Japan. Also, the United States did not use an atomic bomb on Tokyo.