Which event preceded the revolutions of 1989?

Choices were not presented. However, I have encountered this question before and if the choices have been the same then the event that preceded the revolutions of 1989 was that:

Gorbachev made reforms in the Soviet Union.

He initiated the policies of glasnost (openness) and perestroika (restructuring). He also removed the constitutional role of the Communist Party in governing the state which led to the dissolution of the Soviet Union.