Which of the following increased tension between america and the soviet union after world war ii?

the soviets refused to allow elections in eastern european nations.
the soviets insisted on having veto power in the united nations.
the united states refused to recognize communism as a legitimate form of government.
the united states conducted nuclear explosive tests in the atmosphere above the soviet union.

The Soviets refused to allow free elections in Eastern European nations.

When Roosevelt, Churchill and Stalin, leaders of the World War II Allied nations, met at Yalta in 1945, there was a big push for Stalin to allow free elections to take place in the nations of Europe after the war. At that time Stalin agreed, but there was a strong feeling by the other leaders that he might renege on that promise. The Soviets never did allow those free elections to occur. Later, Winston Churchill wrote, ""Our hopeful assumptions were soon to be falsified." Stalin and the Soviets felt they needed the Eastern European nations as satellites to protect their own interests.