Triple

Target entity: Congress of Berlin (1878)
Context triple: [Russo-Turkish War (1877–1878) campaigns, consequence, Congress of Berlin (1878)]

• A. Congress of Berlin chosen
  The Congress of Berlin was an 1878 diplomatic meeting of the great European powers that redrew the map of the Balkans and revised the Treaty of San Stefano following the Russo-Turkish War.
• B. Crimean Conference
  The Crimean Conference, commonly known as the Yalta Conference, was a pivotal 1945 World War II meeting where Roosevelt, Churchill, and Stalin negotiated the postwar reorganization of Europe.
• C. Treaty of Berlin 1878
  The Treaty of Berlin of 1878 was an international agreement that revised the Treaty of San Stefano and restructured the Balkans after the Russo-Turkish War, redefining borders and the status of several states in Southeast Europe.
• D. Belgrade Conference
  The Belgrade Conference was the 1961 gathering of leaders from newly independent and developing countries that launched the Non-Aligned Movement during the Cold War.
• E. Berlin Conference
  The Berlin Conference was an 1884–1885 meeting of European powers in Berlin that formalized the partition of Africa and set the rules for colonial expansion on the continent.
• F. None of above.
• G. Unsure - the case is ambiguous/there is not enough information to decide.