D. The Soviet Union was forced to improve United States–Soviet relation
Nixon opening diplomatic relations with China began with recognition of Communist China. In doing this, it demonstrated the US's willingness to ease Cold War tension which required the USSR to respond the same. The USSR viewed the US-China meetings as the US being willing to accept communism as a government/economic system that they could work with. Presidents following Nixon (Ford and Carter) would continue by opening discussions with the USSR.