Answer: 4 is correct (geographically containing Communism).
Explanation: In contrast to USA, USSR got extremely popular after the WW II. USSR not only won the war, but it was also a revolutionary regime that preached a totally just society, and elimination of bourgeoisie. USSR got very popular already in 1917 and then after 1945. This popularity was extremely high especially where Russian played a role of liberator (Eastern Europe). This favourable moment wanted USSR take advantage of also in Far East (Popular Republic of China was proclaimed in 1949). USA wanted to contain this expansion (Korea, Vietnam).