Answer:
B. Russia stays in WW1.
Step-by-step explanation:
The Bolshevik regime was the consequence of a coup d'etat of the Bolsheviks, a far left group from Russian Social Democrat Workers' Party, that defended land collectivization and cease war hostilities, against the Russia Provisional Government, a liberal-socialist coalition led by Aleksandr Kerensky, in October/November 1917. In consequence, a Communist regime of Marxist-Leninist orientation was established then and later became a Communist state with the rise of Union of Soviet Socialist Republics in 1922, after five years of a bloody civil war held against Whites (Tsarists, Conservative, some Liberals), Greens (Russian peasants with anarchosocialist tendencies), Blacks (Ukranian anarchists) and Nationalists (i.e. Armenians, Moldovans).
The Bolshivik regime signs the Brest-Litovsk Treaty with the German Empire and the Austro-Hungarian Empire on March 3, 1918, which Russia ceded territories in Ukraine, Poland, Lithuania, Estonia, Latvia, Besarabia and Poland and Russia stopped fighting in World War I.
Hence, the option B is NOT an effect of the Bolsheviks Revolution.