C. It weakened Communist control of the Soviet Union.
The intent of the perestroika (restructuring) reforms as well as glasnost (openness) policies introduced in the USSR by Mikhail Gorbachev were to revitalize a floundering Soviet system. However, the efforts had the opposite effect, opening up movements away from and against the communist control of the country. The sort of reforms suggested by Gorbachev also took hold in communist countries in Eastern Europe. By the end of the 1980s there was a massive turn away from communism in Eastern Europe and ultimately in the USSR itself, which dissolved its government in 1991.