B because after the Bolshevik revolution, there was a civil war between the Bolsheviks and the White Movement (and some other minor factions like anarchist Ukraine and the green peasant armies)
The correct answer among all the other choices is C. Advancements in travel and communication allowed this change. This is the statement that does not describe the 20th Amendment. Thank you for posting you question. I hope this answer helped you. Let me know if you need more help.