The Split That Developed Between China and the Soviet Union

The split that developed between China and the Soviet Union in the 1960s was based upon all of the following issues except

A) their rivalry for ideological leadership of the Communist world.
B) disputes over the lands of inner Asia into which the U.S.S.R. had expanded in the age of the tsars.
C) Mao's accusation that Khrushchev had vacillated during the Cuban missile crisis of 1962.
D) the U.S.S.R.'s refusal to support the Vietnamese intervention in Cambodia.