Uhhh the 2nd one? i believe its supposed to be B. But anyway the creation of an atomic bomb.
Explanation:
But the Manhattan project was started around 1938, authorized by President Roosevelt. Leo slizard and einstein gave the idea for the project to create a weapon of mass destruction. After approval a team of various scientists worked on the weapon after completion in 1941. The first successful test was in 1945 in new mexico. Which were later then used on 2 japanese cities.
