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

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

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

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

D. During World War II, the two countries were allies; afterward, the countries were enemies