C) Winston Churchill brought along his political opponent due to election results not being in yet.
Explanation:
The Potsdam Conference ran from July 17 to August 2, 1945. Before the congress, the polls had taken place on 5 July 1945, but Winston Churchill, waiting for the collecting of the vote of the Service, pulled Clement Attlee away from Potsdam, his political opponents. On the 25th of the same month, they were both back home waiting for the following morning's findings. It was clear by afternoon that the party was won by Clement Attlee. This led to Winston Churchill's resignation as Prime Minister and to his substitution at the Potsdam Conference by Clement Attlee.
