Answer:
D. democratization of the political system.
Explanation:
By 1988, Soviet leader Mikhail Gorbachev expanded his reforms to include the "democratization of the political system."
Mikhail Gorbachev was known as the Chairman of the Presidium of the Supreme Soviet of the Soviet Union. During his time, he made so many reforms that show democratic principles and political systems, such as allowing multi-party elections to hold during this period.
He also allowed the unification of Germany through democratic principles.
