The correct answer is option 'C', Gorbachev.

Gorbachev was the leader of the Soviet Union from 1985 to 1991. During his tenure, he implemented a series of policies aimed at reforming and democratizing the Soviet Union. These policies, collectively known as perestroika (restructuring) and glasnost (openness), were aimed at addressing the economic and political stagnation that had plagued the country for decades.

Under Gorbachev's leadership, the Soviet Union sought to normalize its relations with the West and improve its image on the international stage. This was a departure from the previous policy of confrontation and isolationism that had characterized the Soviet Union's approach to the West.

Gorbachev initiated a series of arms control negotiations with the United States, which eventually led to the signing of the Intermediate-Range Nuclear Forces Treaty in 1987. This treaty was the first to eliminate an entire class of nuclear weapons and represented a significant step towards reducing tensions between the two superpowers.

Internally, Gorbachev introduced political reforms aimed at increasing transparency and accountability within the Soviet system. He encouraged greater freedom of speech and press, allowing for more open discussions and criticisms of the government. This led to a relaxation of censorship and the emergence of a more vibrant civil society.

Gorbachev also sought to decentralize power within the Soviet Union by devolving more authority to the individual republics that made up the country. This was a significant departure from the centralized command economy that had characterized the Soviet system for decades.

However, Gorbachev's reforms ultimately led to unintended consequences. The loosening of political control and the opening up of the media allowed for greater criticism of the Soviet regime, which undermined its legitimacy. Additionally, the economic reforms introduced under perestroika resulted in widespread economic hardship and led to increased demands for independence from the various republics within the Soviet Union.

In 1991, the Soviet Union dissolved, and Gorbachev resigned as its leader. While his reforms ultimately led to the end of the Soviet Union, Gorbachev is often credited with initiating a period of significant change and opening up the possibility for a more democratic and transparent system in Russia.