Answer:
The correct answer is A. In the late 1980s to early 1990s, Eastern Europe experienced governmental upheavals, protests and significant changes. These changes were called the "Revolutions of 1989".
Step-by-step explanation:
The Revolutions of 1989 were part of a revolutionary wave that swept Central and Eastern Europe in the fall of 1989, causing the overthrow of Soviet-style socialist states within a few months.
Political turmoil began in Poland, and led to a wave of mostly peaceful revolutions in East Germany, Czechoslovakia, Hungary, and Bulgaria. Romania was the only country of the Eastern Bloc that violently overthrew its communist regime and executed its head of state.
The Revolutions of 1989 greatly changed the balance of power in the world and marked (along with the subsequent dissolution of the Soviet Union) the end of the Cold War and the beginning of the Post-Cold War era.