C seems to be right a is totally wrong
The answer is: b. The Soviet Union fell apart
Before Gorbachev's reforms exist, several territories in soviet union was united under one principle of communism.
When the Gorbachev's reforms were created, the soviet union started to adopt some of democratic and free market value that adopted by countries in western hemisphere.
When this happen, the bind that united territories in the soviet union no longer exist. This became one of the factors that caused the soviet union to fell apart.
C. population
There are more representatives in the court for areas that are more densely populated so that the population/representative ratio remains comparative.
