Refer to the passage. "During World War II, the Communist Party of the Soviet Union partially abandoned an approach to international relations which presupposed the inevitability of a clash between communism and capitalism. Since the end of the war, however, Soviet publicists have revived three persistent themes of Marxist thinking—the inevitability of: (1) a revolutionary class struggle within each capitalist country; (2) conflicts between capitalistic Powers; and (3) intervention in Soviet affairs by the capitalistic Powers. Recent authoritative Soviet statements have cited a speech made by Stalin in 1928 in which he clearly enunciated these themes. Stalin’s recent electoral addresses, as well as those of other members of the Politburo of the Communist Party, attacked capitalism as a breeder of world conflicts and clearly indicated that the goal of Soviet postwar economic planning is the strengthening of the Soviet war potential.”

"Soviet Policy toward the Western Powers,” an internal White House memorandum concerning Soviet foreign policy, April 4, 1946

According to the memorandum, which of the following best explains the root of the tensions between the Soviet Union and the United States?

The building of the Berlin Wall to divide the former German capital into West and East occupation zones
The successful launch of Sputnik I, the first successful artificial satellite, by the Soviet Union
The inherent conflict between capitalist and communist economic policies, markets, and trade
The Soviet fear of world conflicts due to interference from the United States in communist nations