The correct option is D Perestoika
Mikhail Gorbachev came into power in 1985 as the General Secretary of Soviet Union. He introduced Glasnost, a policy that would introduced transparency in government dealings. Perestorika, on the other hand, was a policy for the reconstruction of the Soviet Union. His efforts to democratize his country’s political system and decentralise the economy of Soviet Union led to its eventual breakup and downfall. In part, he ended the Soviet Union's post-war domination of Eastern Europe.