The First Serious Threat to the Red Army During the Russian

The first serious threat to the Red Army during the Russian Civil War came from​

A) ​White army factions in Siberia.
B) ​Peasantry refusing to supply the Red Army after the Treaty of Brest Litovsk.
C) ​German forces seeking to mobilize through Bulgaria.
D) ​the last ditch attempt by the Ottoman Empire to maintain control in the Caucauses region.
E) ​Allied troops working against the Bolsheviks to bring the Russians back to World War I.