Which of the following events belongs in box b on the chart above?
a. the creation of the european union
b. the russian revolution
c. the break-up of the ussr
d. the cold war

The event that belongs to Box B on the chart is D, the Cold War.

Explanation:

The Cold War was the conflict between the Western Bloc, under the leadership of the United States of America, and the Eastern Bloc under the leadership of the Soviet Union, from 1947 to 1989. There never was a direct military conflict between the superpowers USA, the Soviet Union and their respective military blocs, but there were proxy wars, such as the Korean War and the war in Afghanistan.

The Cold War emerged as a systemic confrontation between capitalism and communism, and determined foreign and security policy worldwide in the second half of the 20th century. For decades, political, economic, technical and military efforts were made on both sides to stem or repress the influence of the other side worldwide.

The conflict took on extremely threatening three times, so that the possibility of a "hot" war between the superpowers was approaching: in the Berlin blockade of 1948/49, in the Cuban missile crisis of 1962 and in the dispute over the medium-range missiles from 1979 to 1982/83. Between these phases, there were periods of less conflict intensity or relaxation.  

The competition between the two systems was also reflected in the proliferation of ideological propaganda by the superpowers and their allies, in their arms race, in economic development, and in developments in the areas of culture, sport, science and technology.

d is the logical answer but im not a 100% sure