Which of the following helped Mao Zedong's communist forces defeat the Nationalist government during the Chinese Civil War?

A. Communist forces controlled nearly all of China's largest and most industrialized urban centers.
B. Communist propaganda convinced many Chinese that the government was a corrupt dictatorship.
C. The United States agreed to allow the communists to control northern China after World War II.
D. The Soviet Union threatened to use nuclear weapons against the Nationalists if they did not surrender.