Pls help 10 pts What happened at the end of the Cold War?

a. The Soviet Union agreed to join the United States in a war against Russia.

b. The United States agreed to accept Communism as an alternative economic system.

c. The Soviet Union began allowing more economic and political freedoms for their citizens, which led to the collapse of the Soviet Union.

d. The United States began trading with the Soviet Union and was forced by American businesses to accept the end of the Cold War. ​