(A) They refused to go
(B) They were neutral
(C) ** The Treaty of Brest-Litovsk
(D) They were having internal problems
EXPLANATIONS BELOW
Concept note-1: -Russia had fought as one of the Allies until December 1917, when its new Bolshevik Government withdrew from the war. The Allied Powers refused to recognize the new Bolshevik Government and thus did not invite its representatives to the Peace Conference.
Concept note-2: -Treaty of Versailles Terms Also absent was Russia, which had fought as one of the Allied powers until 1917, when, following the Russian Revolution, the country’s new Bolshevik government concluded a separate peace with Germany and withdrew from the conflict.
Concept note-3: -On March 3 the Soviet government accepted a treaty by which Russia lost Ukraine, its Polish and Baltic territories, and Finland. (Ukraine was recovered in 1919, during the Russian Civil War.) The treaty was ratified by the Congress of Soviets on March 15.
Concept note-4: -Finally, the eradication of the early treaty through the Treaty of Versailles allowed Russia the opportunity to move west and try to reclaim its ceded territory. It automatically received the land back within its borders, but there were other countries before Brest-Litovsk that was also part of the Russian Empire.