In the 1950s and 1960s What Happened to the Relationship

In the 1950s and 1960s what happened to the relationship between the Soviet Union and Mao Zedong's China?

A) It remained unchanged.
B) It was altered by the Soviet Union's increased interest in increasing world tensions,especially with the militarily dangerous United Nations.
C) It was weakened by Mao Zedong's belief that,after Stalin's death,Mao's status as the most experienced Marxist ruler should make him the leading socialist.
D) It was destroyed by Mao's threat to occupy southeastern Siberia if the Soviet government continued to make,test,and store nuclear weapons there.
E) It improved because of a joint fear of the United States' ambitions in South Asia.