Answer:
C. command . . . market
Step-by-step explanation:
Russia and the majority of the countries of the eastern half of Europe, as well as part of Central Europe, are in the process of transitioning from command economies to market economies.
All of the countries that are or were until recently in this process are countries that were socialist or communist until the early 1990's. The Soviet Union, Yugoslavia, and multiple other nations in between them were all under socialist or communist rule, which also meant that they had command economies.
When the socialist and communist governments fell though, the people wanted changes, and one of those changes were that the economies become market ones. The reason for this was that the people wanted to choose what to produce, to choose what to buy and consume, to be able to develop their own businesses and implement their ideas on the market, and of course to open up and connect to the rest of the world.