Final answer:
Russians were uncomfortable with the rapid changes in the 1980s due to social upheaval caused by the Soviet Union's political and economic reforms, which eventually led to its collapse.
Step-by-step explanation:
One reason why Russians were uncomfortable with the rapid changes occurring in their country in the 1980s is D. Social upheaval. The introduction of policies such as 'glasnost' (openness) and 'perestroika' (restructuring) by Premier Mikhail Gorbachev aimed to reform the Soviet Union but these changes also led to the loss of control over Eastern European countries and the eventual collapse of the Soviet Union in 1991. This period was marked by significant economic, political, and social changes that were too rapid for many Russians to adapt to comfortably, leading to feelings of instability and uncertainty about the future.