Answer: B. They decided the Soviet Union should enter the war against Japan
Explanation: The Yalta Conference, code-named the Argonaut Conference, held between February 4–11, 1945, was the World War II meeting of the heads of government of the United States, the United Kingdom, and the Soviet Union(Big Allied Three) to discuss the postwar reorganization of Germany and Europe.
However, each of the three leaders had his own agenda for post-war Germany and liberated Europe. Roosevelt wanted Soviet support in the U.S. Pacific War against Japan (Operation August Storm), as well as Soviet participation in the United Nations, Churchill pressed for free elections and democratic governments in Eastern and Central Europe while Stalin demanded a Soviet sphere of political influence in Eastern and Central Europe.