The answer is C. Glasnost.
Glasnost was taken to mean increased openness and transparency in government institutions and activities in the Soviet Union (USSR). Glasnost apparently reflected a commitment to getting Soviet citizens to discuss publicly the problems of their system and seek solutions.
Perestroika and Glasnost were a new policies introduced by the Mikhail Gorbachev , the Former General Secretary of the Communist Party of the Soviet Union during the 1990s.
This is the correct answer for APEX
The correct answer is Détente
The concept of détente is linked to the new arrangements of the late 1960s and the 1970s. The erosion of the ideological monolithism of the two blocs has given a new connotation to international relations. In addition to adversaries, the USA and the USSR have presented themselves as partners.
Conflicts would no longer focus on direct rivalry between the two powers and would go beyond disputes in Asia, Africa and the Middle East.
Furthermore, it is during this period that negotiations on the limitations of nuclear weapons are established.