Answer:
B. Seizure of power by the Bolsheviks (Reds)
Step-by-step explanation:
Once Lenin had gained power and established the USSR (Soviet Union) he fulfilled his promise to the Russian people of ending Russian participation in WW1. The Russian Bolsheviks and Germans signed the Treaty of Brest-Litovsk which took the USSR out of WW1 in exchange for territory and war reparations.