Answer:
C
Step-by-step explanation:
After the Bolsheviks launched the October Uprising, taking control of the government, Russia was launched into an immediate civil war. This fact coupled with the heavy economic strain of WWI caused the Bolsheviks to seek peace terms with the Central Powers. Signing the treaty of Treaty of Brest-Litovsk, the newly formed Communist Russia ceded much of its Western territories including much of Belarus, Ukraine, all of the Baltics, Finland and Poland as well several cities and towns along its southern border with the Ottomans. With this treaty signed, Russia had officially left the war, giving up large swathes of territory in exchange for peace.