B. From Asia to Europe-the shift of the focus of the Cold War C. From tension to relaxation-the new trend of Sino-Soviet relations D. On the rise of the European Union and the shake of American hegemony This topic examines the evolution of international relations in the 1970s. In the 1970s, with the combination of Western Europe, the strengthening of Japanese economic strength and China's return to the United Nations, the bipolar pattern in international relations was gradually impacted and the trend of multipolarization appeared. So item a is the most suitable. Option BC does not conform to historical facts, and the establishment of the European Union in item D was in the 1990s.