(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.