The correct answer is D. At the Yalta Conference, the Allies decided that they would temporarily divide Germany among the Allies in order to help rebuild it.
The Yalta Conference was the meeting held before the end of the Second World War (February 4 to 11, 1945) by Joseph Stalin, Winston Churchill and Franklin D. Roosevelt, as heads of government of the Soviet Union, the United Kingdom and the United States, respectively.
Regarding the future of Germany, the Conference was extremely ambiguous. The Allies only committed to the aforementioned disarmament, demilitarization and division, thus allowing future changes and giving free rein for each of the parties to interpret it to their liking. However, Germany was divided into four sectors, one for each ally, to avoid a new resurgence of the Nazi movement.