The outcome which is the agreement to have the Soviet Union join other allies in the war against japan was most essential in the Yalta conference.
The Yalta Conference was a Conference between World War II allies where they discuss conditions under which the Soviet Union would enter the war against Japan
Hence, the outcome which is the agreement to have the Soviet Union join other allies in the war against japan was most essential in the Yalta conference.
Therefore, the Option D is correct.
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