(MC)The diagram below shows events that took place in the spring and summer of 1945:

A timeline diagram runs from left to right with four boxes. The first box reads, Germany surrenders to end the war in Europe. The second box reads, The U.S. conducts its first successful test of an atomic bomb. The third box reads, Potsdam Conference is held by the Allied Powers. The fourth box has a question mark.

Which of the following completes the diagram?

The United States drops two atomic bombs on Japan.
Soviet Premier Stalin refuses to aid the U.S. effort to invade Japan.
The Soviet Union conducts its first successful test of an atomic bomb.
The Allied powers agree to use atomic weapons to force a Japanese surrender.

The United States dropped two atomic bombs on Japan on 6 August 1945 in Hiroshima and 9 August 1945 in Nagasaki. Those were the first and only times that nuclear weapons were used in warfare and these events put an end to WWII. The dropping of the nuclear bombs happened a few days after the Potsdam Conference that took place between 17 July and 2 August 1945, where the allies leaders from the US, the UK, and the USSR, met after the defeat of Nazi Germany. The dropping of the two atomic bombs finished establishing the US as a global military superpower and marked the start of the nuclear race between the US and the USSR.