How did the relationship between the U.S. and Soviet Union change in the decade following World War II?

ADuring World War II, neither country built atomic or nuclear weapons; afterward, both of them built these weapons

BDuring World War II, the two countries fought against each other directly with weapons, afterward, they did not

CDuring World War II, both countries were democracies; afterward, the Soviet Union became a dictatorship

DDuring World War II, the two countries were allies; afterward, the countries were enemies