The tension between Moscow and Beijing, which started at the beginning of the 1960s, softened in the mid-1980s. In 1991, the Sino-Russian rapprochement continued after the dissolution of the Soviet Union. After the PRC resolved territorial disputes with neighboring CIS states (Russia, Kazakhstan, Kyrgyzstan, and Tajikistan), it became possible to further develop regional cooperation. Another reason for Sino-Russian converges is economic interests, and balancing the US was also the cornerstone of post-1990 Chinese and Russian relations. Russia perceived threat because of the NATO’s expansions to Eastern Europe, while China was disturbed by the bust of the US on human rights and its trade with Taiwan.

The correct choice is C.