A

When the Soviet Union became weak, countries that supported it faced a sudden decrease in support for Socialist and Communist parties. This resulted in the development of democratic values all over Europe.

Explanation:

The Soviet Union was a prominent power in Eurasia, and thus its weakening had a noticeable effect on European countries. This was mainly because most of Eastern Europe was under the iron curtain during the Cold War.

The most affected countries were the ones that engaged in the Warsaw Pact. This pact was designed to counteract the foreign power NATO and thus led to the opposition between Eastern Europe and the West.

The Soviet Union and Europe in 1949-1989 map.
Source: https://qph.fs.quoracdn.net

People also opposed the authoritarian politics used by Soviet leaders, and thus their focus shifted on human rights and freedoms. The weakening of the Soviet Union also led to a reduction in military tensions in European countries, particularly those close to the iron curtain.