The Soviet Union ceased to exist in December 1991 due in part to: Gorbachev's reforms, leading to the end of the Communist party the Boris Yeltsin-led coup of the government the Communists winning more seats than the reformers

The right answer for the question that is being asked and shown above is that: "the Boris Yeltsin-led coup of the government." The Soviet Union ceased to exist in December 1991 due in part to the Boris Yeltsin-ledcoup of the government