Answer:
The group that supported Communists during the Russian Civil War: Reds.
A radical political party that believed a revolution was the only way to bring about change in czartist Russia: Bolsheviks.
The group that supported czarists during the Russian Civil War: Whites.
Step-by-step explanation:
The reds were groups that supported the Soviet, regime held by the Bolsheviks.
The bolsheviks were a faction of the Russian Socialdemocrat Party, which considered that Czarist regime could be only ended by means of revolution, violence and nationalization of land.
The whites were groups that supported Czarists in the Russian Civil War.